OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..3260
FORMULA
a(n) = [x^n] (1-x)^n / Product_{j=2..n} (1-x^j).
a(n) ~ (-1)^n * exp(Pi*sqrt(n/3)/2 + Pi^2/96) * 2^(n - 1/2) / (sqrt(3)*n). - Vaclav Kotesovec, May 07 2018
MAPLE
b:= proc(n, i, k) option remember; `if`(n=0 or i<2,
binomial(k+n-1, n), add(b(n-i*j, i-1, k), j=0..n/i))
end:
a:= n-> b(n$2, -n):
seq(a(n), n=0..35);
# second Maple program:
b:= proc(n, k) option remember; `if`(n=0, 1, add(
(numtheory[sigma](j)+k-1)*b(n-j, k), j=1..n)/n)
end:
a:= n-> b(n, -n):
seq(a(n), n=0..35);
# third Maple program:
b:= proc(n, k) option remember; `if`(n=0, 1, `if`(k=1,
combinat[numbpart](n), b(n, k+1)-b(n-1, k+1)))
end:
a:= n-> b(n, -n):
seq(a(n), n=0..35);
MATHEMATICA
Table[SeriesCoefficient[(1 - x)^n*Product[1/(1 - x^k), {k, 2, n}], {x, 0, n}], {n, 0, 30}] (* Vaclav Kotesovec, May 07 2018 *)
b[n_, k_] := b[n, k] = If[n == 0, 1, If[k == 1, PartitionsP[n], b[n, k + 1] - b[n - 1, k + 1]]]; Table[b[n, -n], {n, 0, 40}] (* Vaclav Kotesovec, May 07 2018, after Alois P. Heinz *)
CROSSREFS
KEYWORD
sign
AUTHOR
Alois P. Heinz, Sep 18 2017
STATUS
approved