VOOZH about

URL: https://oeis.org/A328776

⇱ A328776 - OEIS

login
A328776
Product_{n>=1} (1 + x^n)^a(n) = 1 + Sum_{n>=1} sigma(n) * x^n, where sigma = A000203.
2
1, 3, 1, 3, -3, 2, -1, 4, 3, -8, -1, 6, 3, -4, -7, 12, 1, -6, 7, 0, -13, -13, 27, 13, -19, -11, 11, -21, -25, 191, -81, -300, 89, 327, 325, -745, -275, 579, -255, 1287, -453, -2075, -583, 2142, 5985, -6698, -6661, 6981, 3045, 3857, -7205, -2784, -5447, -4891, 48547
OFFSET
1,2
COMMENTS
Inverse weigh transform of A000203.
MATHEMATICA
b[n_, i_] := b[n, i] = If[n == 0, 1, If[i < 1, 0, Sum[Binomial[a[i], j] b[n - i j, i - 1], {j, 0, n/i}]]]; a[n_] := a[n] = DivisorSigma[1, n] - b[n, n - 1]; Array[a, 55]
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Oct 27 2019
STATUS
approved