500 (number)

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← 499 500 501 →
Cardinalfive hundred
Ordinal500th
(five hundredth)
Factorization22 × 53
Greek numeralΦ´
Roman numeralD
Binary1111101002
Ternary2001123
Octal7648
Duodecimal35812
Hexadecimal1F416

500 (five hundred) is the natural number following 499 and preceding 501.

Mathematical properties[edit]

500 = 22 × 53. It is a Harshad number, meaning divisible by the sum of its digits.

Other fields[edit]

Five hundred is also

Slang names[edit]

  • Monkey (UK slang for £500; USA slang for $500)[1]

Integers from 501 to 599[edit]

500s[edit]

501[edit]

501 = 3 × 167. It is:

  • the sum of the first 18 primes (a term of the sequence OEISA007504).
  • palindromic in bases 9 (6169) and 20 (15120).

502[edit]

503[edit]

503 is:

504[edit]

504 = 23 × 32 × 7. It is:

505[edit]

506[edit]

506 = 2 × 11 × 23. It is:

507[edit]

  • 507 = 3 × 132

508[edit]

  • 508 = 22 × 127, sum of four consecutive primes (113 + 127 + 131 + 137).

509[edit]

509 is:

510s[edit]

510[edit]

510 = 2 × 3 × 5 × 17. It is:

  • the sum of eight consecutive primes (47 + 53 + 59 + 61 + 67 + 71 + 73 + 79).
  • the sum of ten consecutive primes (31 + 37 + 41 + 43 + 47 + 53 + 59 + 61 + 67 + 71).
  • the sum of twelve consecutive primes (19 + 23 + 29 + 31 + 37 + 41 + 43 + 47 + 53 + 59 + 61 + 67).
  • a nontotient.
  • a sparsely totient number.[12]
  • a Harshad number.

511[edit]

511 = 7 × 73. It is:

512[edit]

512 = 83 = 29. It is:

513[edit]

513 = 33 × 19. It is:

  • palindromic in bases 2 (10000000012) and 8 (10018)
  • a Harshad number
  • Area code of Cincinnati, Ohio

514[edit]

514 = 2 × 257, it is:

515[edit]

515 = 5 × 103, it is:

  • the sum of nine consecutive primes (41 + 43 + 47 + 53 + 59 + 61 + 67 + 71 + 73).

516[edit]

516 = 22 × 3 × 43, it is:

517[edit]

517 = 11 × 47, it is:

  • the sum of five consecutive primes (97 + 101 + 103 + 107 + 109).
  • a Smith number.[16]

518[edit]

518 = 2 × 7 × 37, it is:

  • = 51 + 12 + 83 (a property shared with 175 and 598).
  • a sphenic number.
  • a nontotient.
  • an untouchable number.[15]
  • palindromic and a repdigit in bases 6 (22226) and 36 (EE36).
  • a Harshad number.

519[edit]

519 = 3 × 173, it is:

  • the sum of three consecutive primes (167 + 173 + 179)
  • palindromic in bases 9 (6369) and 12 (37312).

520s[edit]

520[edit]

520 = 23 × 5 × 13. It is:

521[edit]

521 is:

  • a Lucas prime.[17]
  • A Mersenne exponent, i.e. 2521−1 is prime.
  • a Chen prime.
  • an Eisenstein prime with no imaginary part.
  • palindromic in bases 11 (43411) and 20 (16120)

522[edit]

522 = 2 × 32 × 29. It is:

  • the sum of six consecutive primes (73 + 79 + 83 + 89 + 97 + 101).
  • a repdigit in bases 28 (II28) and 57 (9957).
  • a Harshad number.

523[edit]

523 is:

  • a prime number.
  • the sum of seven consecutive primes (61 + 67 + 71 + 73 + 79 + 83 + 89).
  • palindromic in bases 13 (31313) and 18 (1B118).

524[edit]

524 = 22 × 131

525[edit]

525 = 3 × 52 × 7. It is:

  • palindromic in base 10 (52510).
  • the number of scan lines in the NTSC television standard.
  • a self number.

526[edit]

526 = 2 × 263, centered pentagonal number,[19] nontotient, Smith number[16]

527[edit]

527 = 17 × 31. it is:

  • palindromic in base 15 (25215).
  • also, the section of the US Tax Code regulating soft money political campaigning (see 527 groups)

528[edit]

528 = 24 × 3 × 11. It is:

529[edit]

529 = 232. It is:

530s[edit]

530[edit]

530 = 2 × 5 × 53. It is:

531[edit]

531 = 32 × 59. It is:

  • palindromic in base 12 (38312).
  • a Harshad number.

532[edit]

532 = 22 × 7 × 19. It is:

  • a pentagonal number.[21]
  • a nontotient.
  • palindromic and a repdigit in bases 11 (44411), 27 (JJ27), and 37 (EE37).

533[edit]

533 = 13 × 41. It is:

  • the sum of three consecutive primes (173 + 179 + 181).
  • the sum of five consecutive primes (101 + 103 + 107 + 109 + 113).
  • palindromic in base 19 (19119).

534[edit]

534 = 2 × 3 × 89. It is:

  • a sphenic number.
  • the sum of four consecutive primes (127 + 131 + 137 + 139).
  • a nontotient.
  • palindromic in bases 5 (41145) and 14 (2A214).

535[edit]

535 = 5 × 107. It is:

for ; this polynomial plays an essential role in Apéry's proof that is irrational.

535 is used as an abbreviation for May 35, which is used in China instead of June 4 to evade censorship by the Chinese government of references on the Internet to the Tiananmen Square protests of 1989.[22]

536[edit]

536 = 23 × 67. It is:

  • the number of ways to arrange the pieces of the ostomachion into a square, not counting rotation or reflection.
  • a refactorable number.[8]
  • the lowest happy number beginning with the digit 5.

537[edit]

537 = 3 × 179, Mertens function (537) = 0

538[edit]

538 = 2 × 269. It is:

539[edit]

539 = 72 × 11

540s[edit]

540[edit]

540 = 22 × 33 × 5. It is:

541[edit]

541 is:

Mertens function(541) = 0.

542[edit]

542 = 2 × 271. It is:

543[edit]

543 = 3 × 181; palindromic in bases 11 (45411) and 12 (39312).

544[edit]

544 = 25 × 17.

545[edit]

545 = 5 × 109. It is:

546[edit]

546 = 2 × 3 × 7 × 13. It is:

  • the sum of eight consecutive primes (53 + 59 + 61 + 67 + 71 + 73 + 79 + 83).
  • palindromic in bases 4 (202024), 9 (6669), and 16 (22216).
  • a repdigit in bases 9 and 16.

547[edit]

547 is:

548[edit]

548 = 22 × 137. It is:

Also, every positive integer is the sum of at most 548 ninth powers;

549[edit]

549 = 32 × 61, it is:

  • a repdigit in bases 13 (33313) and 60 (9960).

550s[edit]

550[edit]

550 = 2 × 52 × 11. It is:

551[edit]

551 = 19 × 29. It is:

  • It is the number of mathematical trees on 12 unlabeled nodes. [34]
  • the sum of three consecutive primes (179 + 181 + 191).
  • palindromic in base 22 (13122).
  • the SMTP status code meaning user is not local

552[edit]

552 = 23 × 3 × 23. It is:

  • the sum of six consecutive primes (79 + 83 + 89 + 97 + 101 + 103).
  • the sum of ten consecutive primes (37 + 41 + 43 + 47 + 53 + 59 + 61 + 67 + 71 + 73).
  • a pronic number.[10]
  • an untouchable number.[15]
  • palindromic in base 19 (1A119).
  • a Harshad number.
  • the model number of U-552.
  • the SMTP status code meaning requested action aborted because the mailbox is full.

553[edit]

553 = 7 × 79. It is:

  • the sum of nine consecutive primes (43 + 47 + 53 + 59 + 61 + 67 + 71 + 73 + 79).
  • the model number of U-553
  • the SMTP status code meaning requested action aborted because of faulty mailbox name.

554[edit]

554 = 2 × 277. It is:

  • a nontotient.
  • the SMTP status code meaning transaction failed.

Mertens function(554) = 6, a record high that stands until 586.

555[edit]

555 = 3 × 5 × 37 is:

  • a sphenic number.
  • palindromic in bases 9 (6769), 10 (55510), and 12 (3A312).
  • a repdigit in bases 10 and 36.
  • a Harshad number.

556[edit]

556 = 22 × 139. It is:

  • the sum of four consecutive primes (131 + 137 + 139 + 149).
  • an untouchable number, because it is never the sum of the proper divisors of any integer.[15]
  • a happy number.
  • the model number of U-556; 5.56×45mm NATO cartridge.

557[edit]

557 is:

  • a prime number.
  • a Chen prime.
  • an Eisenstein prime with no imaginary part.

558[edit]

558 = 2 × 32 × 31. It is:

  • a nontotient.
  • a repdigit in bases 30 (II30) and 61 (9961).
  • a Harshad number.
  • The sum of the largest prime factors of the first 558 is itself divisible by 558 (the previous such number is 62, the next is 993).
  • in the title of the Star Trek: Deep Space Nine episode "The Siege of AR-558"

559[edit]

559 = 13 × 43. It is:

  • the sum of five consecutive primes (103 + 107 + 109 + 113 + 127).
  • the sum of seven consecutive primes (67 + 71 + 73 + 79 + 83 + 89 + 97).
  • a nonagonal number.[35]
  • a centered cube number.[36]
  • palindromic in base 18 (1D118).
  • the model number of U-559.

560s[edit]

560[edit]

560 = 24 × 5 × 7. It is:

561[edit]

561 = 3 × 11 × 17. It is:

562[edit]

562 = 2 × 281. It is:

  • a Smith number.[16]
  • an untouchable number.[15]
  • the sum of twelve consecutive primes (23 + 29 + 31 + 37 + 41 + 43 + 47 + 53 + 59 + 61 + 67 + 71).
  • palindromic in bases 4 (203024), 13 (34313), 14 (2C214), 16 (23216), and 17 (1G117).
  • the number of Native American (including Alaskan) Nations, or "Tribes," recognized by the USA government.

563[edit]

563 is:

564[edit]

564 = 22 × 3 × 47. It is:

  • the sum of a twin prime (281 + 283).
  • a refactorable number.
  • palindromic in bases 5 (42245) and 9 (6869).

565[edit]

565 = 5 × 113. It is:

  • the sum of three consecutive primes (181 + 191 + 193).
  • a member of the Mian–Chowla sequence.[43]
  • a happy number.
  • palindromic in bases 10 (56510) and 11 (47411).

566[edit]

566 = 2 × 283. It is:

  • nontotient.
  • a happy number.

567[edit]

567 = 34 × 7. It is:

  • palindromic in base 12 (3B312).

568[edit]

568 = 23 × 71. It is:

  • the sum of the first nineteen primes (a term of the sequence OEISA007504).
  • a refactorable number.
  • palindromic in bases 7 (14417) and 21 (16121).
  • the smallest number whose seventh power is the sum of 7 seventh powers.
  • the room number booked by Benjamin Braddock in the 1967 film The Graduate.
  • the number of millilitres in an imperial pint.
  • the name of the Student Union bar at Imperial College London

569[edit]

569 is:

  • a prime number.
  • a Chen prime.
  • an Eisenstein prime with no imaginary part.
  • a strictly non-palindromic number.[42]

570s[edit]

570[edit]

570 = 2 × 3 × 5 × 19. It is:

571[edit]

571 is:

  • a prime number.
  • a Chen prime.
  • a centered triangular number.[14]
  • the model number of U-571 which appeared in the 2000 movie U-571

572[edit]

572 = 22 × 11 × 13. It is:

573[edit]

573 = 3 × 191. It is:

574[edit]

574 = 2 × 7 × 41. It is:

  • a sphenic number.
  • a nontotient.
  • palindromic in base 9 (7079).

575[edit]

575 = 52 × 23. It is:

  • palindromic in bases 10 (57510) and 13 (35313).

576[edit]

576 = 26 × 32 = 242. It is:

  • the sum of four consecutive primes (137 + 139 + 149 + 151).
  • a highly totient number.[44]
  • a Smith number.[16]
  • an untouchable number.[15]
  • palindromic in bases 11 (48411), 14 (2D214), and 23 (12123).
  • a Harshad number.
  • four-dozen sets of a dozen, which makes it 4 gross.

577[edit]

577 is:

578[edit]

578 = 2 × 172. It is:

  • a nontotient.
  • palindromic in base 16 (24216).

579[edit]

579 = 3 × 193; it is a ménage number.[46]

580s[edit]

580[edit]

580 = 22 × 5 × 29. It is:

  • the sum of six consecutive primes (83 + 89 + 97 + 101 + 103 + 107).
  • palindromic in bases 12 (40412) and 17 (20217).

581[edit]

581 = 7 × 83. It is:

  • the sum of three consecutive primes (191 + 193 + 197).

582[edit]

582 = 2 × 3 × 97. It is:

  • a sphenic number.
  • the sum of eight consecutive primes (59 + 61 + 67 + 71 + 73 + 79 + 83 + 89).
  • a nontotient.

583[edit]

583 = 11 × 53. It is:

  • palindromic in base 9 (7179).

584[edit]

584 = 23 × 73. It is:

  • an untouchable number.[15]
  • the sum of totient function for first 43 integers.
  • a refactorable number.

585[edit]

585 = 32 × 5 × 13. It is:

  • palindromic in bases 2 (10010010012), 8 (11118), and 10 (58510).
  • a repdigit in bases 8, 38, 44, and 64.
  • the sum of powers of 8 from 0 to 3.

When counting in binary with fingers, expressing 585 as 1001001001, results in the isolation of the index and little fingers of each hand, "throwing up the horns".

586[edit]

586 = 2 × 293.

  • Mertens function(586) = 7 a record high that stands until 1357.
  • it is the number of several popular personal computer processors (such as the Intel pentium).

587[edit]

587 is:

  • a prime number.
  • safe prime.[2]
  • a Chen prime.
  • an Eisenstein prime with no imaginary part.
  • the sum of five consecutive primes (107 + 109 + 113 + 127 + 131).
  • palindromic in bases 11 (49411) and 15 (29215).
  • the outgoing port for email message submission.

588[edit]

588 = 22 × 3 × 72. It is:

  • a Smith number.[16]
  • palindromic in base 13 (36313).
  • a Harshad number.

589[edit]

589 = 19 × 31. It is:

  • the sum of three consecutive primes (193 + 197 + 199).
  • palindromic in base 21 (17121).

590s[edit]

590[edit]

590 = 2 × 5 × 59. It is:

591[edit]

591 = 3 × 197

592[edit]

592 = 24 × 37. It is:

  • palindromic in bases 9 (7279) and 12 (41412).
  • a Harshad number.

593[edit]

593 is:

  • a prime number.
  • a Sophie Germain prime.
  • the sum of seven consecutive primes (71 + 73 + 79 + 83 + 89 + 97 + 101).
  • the sum of nine consecutive primes (47 + 53 + 59 + 61 + 67 + 71 + 73 + 79 + 83).
  • an Eisenstein prime with no imaginary part.
  • a balanced prime.[41]
  • a Leyland prime.
  • a member of the Mian–Chowla sequence.[43]
  • strictly non-palindromic prime.[42]

594[edit]

594 = 2 × 33 × 11. It is:

  • the sum of ten consecutive primes (41 + 43 + 47 + 53 + 59 + 61 + 67 + 71 + 73 + 79).
  • a nontotient.
  • palindromic in bases 5 (43345) and 16 (25216).
  • a Harshad number.

595[edit]

595 = 5 × 7 × 17. It is:

596[edit]

596 = 22 × 149. It is:

  • the sum of four consecutive primes (139 + 149 + 151 + 157).
  • a nontotient.

597[edit]

597 = 3 × 199

598[edit]

598 = 2 × 13 × 23 = 51 + 92 + 83. It is:

  • a sphenic number.
  • palindromic in bases 4 (211124) and 11 (4A411).

599[edit]

599 is:

  • a prime number.
  • a Chen prime.
  • an Eisenstein prime with no imaginary part.

References[edit]

  1. ^ Evans, I.H., Brewer's Dictionary of Phrase and Fable, 14th ed., Cassell, 1990, ISBN 0-304-34004-9
  2. ^ a b c Sloane, N. J. A. (ed.). "Sequence A005385 (Safe primes)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  3. ^ that is, a term of the sequence OEISA034961
  4. ^ that is, the first term of the sequence OEISA133525
  5. ^ since 503+2 is a product of two primes, 5 and 101
  6. ^ since it is a prime which is congruent to 2 modulo 3.
  7. ^ Sloane, N. J. A. (ed.). "Sequence A000073 (Tribonacci numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  8. ^ a b c Sloane, N. J. A. (ed.). "Sequence A033950 (Refactorable numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  9. ^ Sloane, N. J. A. (ed.). "Sequence A000330 (Square pyramidal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  10. ^ a b Sloane, N. J. A. (ed.). "Sequence A002378 (Oblong (or promic, pronic, or heteromecic) numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  11. ^ Sloane, N. J. A. (ed.). "Sequence A100827 (Highly cototient numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  12. ^ Sloane, N. J. A. (ed.). "Sequence A036913 (Sparsely totient numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  13. ^ Sloane, N. J. A. (ed.). "Sequence A061209 (Numbers which are the cubes of their digit sum)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  14. ^ a b Sloane, N. J. A. (ed.). "Sequence A005448 (Centered triangular numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  15. ^ a b c d e f g h i j Sloane, N. J. A. (ed.). "Sequence A005114 (Untouchable numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  16. ^ a b c d e f Sloane, N. J. A. (ed.). "Sequence A006753 (Smith numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  17. ^ Sloane, N. J. A. (ed.). "Sequence A005479 (Prime Lucas numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  18. ^ Dr. Kirkby (May 19, 2021). "Many more twin primes below Mersenne exponents than above Mersenne exponents". Mersenne Forum.
  19. ^ Sloane, N. J. A. (ed.). "Sequence A005891 (Centered pentagonal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  20. ^ Sloane, N. J. A. (ed.). "Sequence A016754 (Odd squares: a(n) = (2n+1)^2. Also centered octagonal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  21. ^ a b Sloane, N. J. A. (ed.). "Sequence A000326 (Pentagonal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  22. ^ Larmer, Brook (October 26, 2011). "Where an Internet Joke Is Not Just a Joke". New York Times. Retrieved November 1, 2011.
  23. ^ Sloane, N. J. A. (ed.). "Sequence A001107 (10-gonal (or decagonal) numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  24. ^ Snorri Sturluson. "Prose Edda". p. 107.
  25. ^ Snorri Sturluson. "Prose Edda". p. 82.
  26. ^ Sloane, N. J. A. (ed.). "Sequence A031157 (Numbers that are both lucky and prime)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  27. ^ Sloane, N. J. A. (ed.). "Sequence A003154 (Centered 12-gonal numbers. Also star numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  28. ^ Sloane, N. J. A. (ed.). "Sequence A001844 (Centered square numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  29. ^ Sloane, N. J. A. (ed.). "Sequence A002407 (Cuban primes)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  30. ^ Sloane, N. J. A. (ed.). "Sequence A003215 (Hex (or centered hexagonal) numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  31. ^ Sloane, N. J. A. (ed.). "Sequence A069099 (Centered heptagonal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  32. ^ Sloane, N. J. A. (ed.). "Sequence A002411 (Pentagonal pyramidal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  33. ^ a b Sloane, N. J. A. (ed.). "Sequence A071395 (Primitive abundant numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  34. ^ "Sloane's A000055: Number of trees with n unlabeled nodes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Archived from the original on 2010-11-29. Retrieved 2021-12-19.
  35. ^ Sloane, N. J. A. (ed.). "Sequence A001106 (9-gonal (or enneagonal or nonagonal) numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  36. ^ Sloane, N. J. A. (ed.). "Sequence A005898 (Centered cube numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  37. ^ Sloane, N. J. A. (ed.). "Sequence A000292 (Tetrahedral numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  38. ^ Sloane, N. J. A. (ed.). "Sequence A000384 (Hexagonal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  39. ^ Higgins, Peter (2008). Number Story: From Counting to Cryptography. New York: Copernicus. p. 14. ISBN 978-1-84800-000-1.
  40. ^ Sloane, N. J. A. (ed.). "Sequence A007540 (Wilson primes)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  41. ^ a b Sloane, N. J. A. (ed.). "Sequence A006562 (Balanced primes)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  42. ^ a b c Sloane, N. J. A. (ed.). "Sequence A016038 (Strictly non-palindromic numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  43. ^ a b Sloane, N. J. A. (ed.). "Sequence A005282 (Mian-Chowla sequence)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  44. ^ Sloane, N. J. A. (ed.). "Sequence A097942 (Highly totient numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  45. ^ Sloane, N. J. A. (ed.). "Sequence A080076 (Proth primes)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  46. ^ Sloane, N. J. A. (ed.). "Sequence A000179 (Ménage numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.
  47. ^ Sloane, N. J. A. (ed.). "Sequence A060544 (Centered 9-gonal (also known as nonagonal or enneagonal) numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-11.