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A255271 G.f.: Product_{k>=1} 1/(1-x^k)^(3*k+1). 4
1, 4, 17, 58, 186, 546, 1532, 4082, 10502, 26096, 63075, 148536, 342096, 771744, 1709299, 3721792, 7978972, 16860328, 35155475, 72393580, 147351112, 296657196, 591141762, 1166570452, 2281101159, 4421781894, 8500806341, 16214549920, 30696683828 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

In general, if g.f. = Product_{k>=1} 1/(1-x^k)^(m*k+c), m > 0, then a(n) ~ (m*Zeta(3))^(m/36 + c/6 + 1/6) * exp(m/12 - c^2 * Pi^4 / (432*m*Zeta(3)) + c * Pi^2 * n^(1/3) / (3 * 2^(4/3) * (m*Zeta(3))^(1/3)) + 3 * (m*Zeta(3))^(1/3) * n^(2/3) / 2^(2/3)) / (A^m * 2^(c/3 + 1/3 - m/36) * 3^(1/2) * Pi^((c+1)/2) * n^(m/36 + c/6 + 2/3)), where A = A074962 = 1.2824271291... is the Glaisher-Kinkelin constant. - Vaclav Kotesovec, Mar 08 2015

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..1000

Vaclav Kotesovec, Graph - The asymptotic ratio

FORMULA

a(n) ~ Zeta(3)^(5/12) * exp(1/4 - Pi^4/(1296*Zeta(3)) + Pi^2 * n^(1/3) / (6^(4/3) * Zeta(3)^(1/3)) + 3^(4/3) * Zeta(3)^(1/3) * n^(2/3) / 2^(2/3)) / (A^3 * 2^(7/12) * 3^(1/12) * Pi * n^(11/12)), where A = A074962 = 1.2824271291... is the Glaisher-Kinkelin constant and Zeta(3) = A002117 = 1.202056903... .

MAPLE

with(numtheory): etr:= proc(p) local b; b:=proc(n) option remember; local d, j; if n=0 then 1 else add(add(d*p(d), d=divisors(j)) *b(n-j), j=1..n)/n fi end end: a:=etr(n-> 3*n+1): seq(a(n), n=0..50); # after Alois P. Heinz

MATHEMATICA

nmax=50; CoefficientList[Series[Product[1/(1-x^k)^(3*k+1), {k, 1, nmax}], {x, 0, nmax}], x]

CROSSREFS

Cf. A005380, A120844, A255803, A255836.

Sequence in context: A121327 A317757 A183924 * A293798 A027075 A202974

Adjacent sequences:  A255268 A255269 A255270 * A255272 A255273 A255274

KEYWORD

nonn

AUTHOR

Vaclav Kotesovec, Mar 07 2015

STATUS

approved

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Last modified June 20 16:26 EDT 2019. Contains 324234 sequences. (Running on oeis4.)