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A000039
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Coefficient of q^(2n) in the series expansion of Ramanujan's mock theta function f(q).
(Formerly M0629 N0230)
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7
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1, -2, -3, -5, -6, -10, -11, -17, -21, -27, -33, -46, -53, -68, -82, -104, -123, -154, -179, -221, -262, -314, -369, -446, -515, -614, -715, -845, -977, -1148, -1321, -1544, -1778, -2060, -2361, -2736, -3121, -3592, -4097, -4696, -5340, -6105, -6916, -7882, -8919, -10123, -11429, -12952, -14580
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OFFSET
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0,2
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REFERENCES
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N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Vaclav Kotesovec, Table of n, a(n) for n = 0..5000 (terms 0..1000 from T. D. Noe)
L. A. Dragonette, Some Asymptotic Formulae for the Mock Theta Series of Ramanujan, Trans. Amer. Math. Soc., 72 (1952), 474-500.
Eric Weisstein's World of Mathematics, Mock Theta Function
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FORMULA
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a(n) ~ -exp(Pi*sqrt(n/3)) / (2*sqrt(2*n)). - Vaclav Kotesovec, Jun 12 2019
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MATHEMATICA
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f[q_, s_] := Sum[q^(n^2)/Product[1+q^k, {k, n}]^2, {n, 0, s}]; Take[CoefficientList[Series[f[q, 100], {q, 0, 100}], q], {1, -1, 2}]
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PROG
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(PARI) a(n)=if(n<0, 0, polcoeff(1+sum(k=1, sqrtint(2*n), x^k^2/prod(i=1, k, 1+x^i, 1+O(x^(2*n)))^2), 2*n))
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CROSSREFS
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A000025(2n)=a(n). Cf. A000199.
Sequence in context: A130714 A130689 A024560 * A302600 A053436 A057546
Adjacent sequences: A000036 A000037 A000038 * A000040 A000041 A000042
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KEYWORD
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sign
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AUTHOR
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N. J. A. Sloane
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EXTENSIONS
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More terms from Eric W. Weisstein
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STATUS
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approved
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