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A007609
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Values taken by the sigma function A000203, listed with multiplicity and in ascending order.
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20
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1, 3, 4, 6, 7, 8, 12, 12, 13, 14, 15, 18, 18, 20, 24, 24, 24, 28, 30, 31, 31, 32, 32, 36, 38, 39, 40, 42, 42, 42, 44, 48, 48, 48, 54, 54, 56, 56, 57, 60, 60, 60, 62, 63, 68, 72, 72, 72, 72, 72, 74, 78, 80, 80, 84, 84, 84, 90, 90, 90, 91, 93, 96, 96, 96, 96, 98, 98
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OFFSET
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1,2
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COMMENTS
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A175192(a(n)) = 1, A054973(a(n)) >= 1. - Jaroslav Krizek, Mar 01 2010
a(n) is the median of the values of A000203(m) from m=1 to m=2n-1. (This needs confirmation as it relies on the assumption that A000203(n) is always bigger than the median of the values A000203(x) from x=1 to x=n.) - Chayim Lowen, May 27 2015
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LINKS
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T. D. Noe, Table of n, a(n) for n = 1..10000
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FORMULA
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a(n) = sigma(A085790(n)). - Jinyuan Wang, Apr 15 2020
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MAPLE
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sort(select(`<=`, map(numtheory:-sigma, [$1..1000]), 1001)); # Robert Israel, Jun 04 2015
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MATHEMATICA
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terms = 68; ClearAll[t]; t[k_] := t[k] = Sort[ Table[ DivisorSigma[1, n], {n, 1, k*terms}]][[1 ;; terms]]; t[k = 2]; While[t[k] != t[k-1], k++]; t[k] (* Jean-François Alcover, Nov 21 2012 *)
With[{nn=80}, Take[Sort[DivisorSigma[1, Range[nn*100]]], nn]] (* Harvey P. Dale, Mar 09 2016 *)
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PROG
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(PARI) list(lim)=select(k->k<=lim, Set(apply(sigma, [1..lim\1]))) \\ Charles R Greathouse IV, Mar 09 2014
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CROSSREFS
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Cf. A000203, A002191 (duplicates removed), A007368, A085790.
Sequence in context: A191775 A047515 A066650 * A285703 A002191 A108348
Adjacent sequences: A007606 A007607 A007608 * A007610 A007611 A007612
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KEYWORD
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nonn,easy,nice
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AUTHOR
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Walter Nissen
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STATUS
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approved
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