login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A248883
Expansion of Product_{k>=1} (1+x^k)^(k^4).
9
1, 1, 16, 97, 457, 2297, 11113, 52049, 235334, 1039886, 4497930, 19074006, 79418883, 325184763, 1311252535, 5212704708, 20449320159, 79231806015, 303428397505, 1149325838320, 4308477305997, 15993198330782, 58815616643170, 214383601754107, 774837953045873
OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..3360 (terms 0..1000 from Vaclav Kotesovec)
Vaclav Kotesovec, A method of finding the asymptotics of q-series based on the convolution of generating functions, arXiv:1509.08708 [math.CO], Sep 30 2015, p. 22.
FORMULA
a(n) ~ 31^(1/12) * exp(1/5 * (31/7)^(1/6) * 6^(2/3) * Pi * n^(5/6)) / (2^(7/6) * 3^(2/3) * 7^(1/12) * n^(7/12)).
a(0) = 1, a(n) = (1/n)*Sum_{k=1..n} A284926(k)*a(n-k) for n > 0. - Seiichi Manyama, Apr 06 2017
G.f.: exp(Sum_{k>=1} (-1)^(k+1)*x^k*(1 + 11*x^k + 11*x^(2*k) + x^(3*k))/(k*(1 - x^k)^5)). - Ilya Gutkovskiy, May 30 2018
MAPLE
b:= proc(n) option remember; add(
(-1)^(n/d+1)*d^5, d=numtheory[divisors](n))
end:
a:= proc(n) option remember; `if`(n=0, 1,
add(b(k)*a(n-k), k=1..n)/n)
end:
seq(a(n), n=0..35); # Alois P. Heinz, Oct 16 2017
MATHEMATICA
nmax=50; CoefficientList[Series[Product[(1+x^k)^(k^4), {k, 1, nmax}], {x, 0, nmax}], x]
PROG
(PARI) x = 'x + O('x^50); Vec(prod(k=1, 50, (1 + x^k)^(k^4))) \\ Indranil Ghosh, Apr 06 2017
(Magma) m:=50; R<x>:=PowerSeriesRing(Rationals(), m); Coefficients(R! ( (&*[(1+x^k)^k^4: k in [1..m]]) )); // G. C. Greubel, Oct 31 2018
CROSSREFS
Column k=4 of A284992.
Sequence in context: A041488 A277225 A265841 * A223902 A264580 A122102
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Mar 05 2015
STATUS
approved