A289565 - OEIS

A289565

Coefficients in expansion of 1/E_2^(1/2).

1, 12, 252, 5664, 133356, 3224952, 79387488, 1978996416, 49797787788, 1262193008556, 32177428972632, 824182154521056, 21193138994244960, 546767126418119352, 14146104826919725632, 366887630982365262144, 9535791498480146879436

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OFFSET

0,2

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..701

FORMULA

G.f.: Product_{n>=1} (1-q^n)^(-A288968(n)/2).

a(n) ~ c / (sqrt(n) * r^n), where r = A211342 = 0.03727681029645165815098078565... is the root of the equation Sum_{k>=1} A000203(k) * r^k = 1/24 and c = 0.535261044779387956394739769118415667289349331646288208543596374426... - Vaclav Kotesovec, Jul 09 2017

MATHEMATICA

nmax = 20; CoefficientList[Series[(1 - 24*Sum[DivisorSigma[1, k]*x^k, {k, 1, nmax}])^(-1/2), {x, 0, nmax}], x] (* Vaclav Kotesovec, Jul 09 2017 *)

CROSSREFS

1/E_k^(1/2): this sequence (k=2), A289566 (k=4), A289567 (k=6), A001943 (k=8), A289568 (k=10), A289569 (k=14).

Cf. A288816 (1/E_2), A288968, A289291 (E_2^(1/2)).

Sequence in context: A367737 A210484 A099139 * A198475 A035013 A065583

Adjacent sequences: A289562 A289563 A289564 * A289566 A289567 A289568

KEYWORD

nonn

AUTHOR

Seiichi Manyama, Jul 08 2017

STATUS

approved