A321068 a(n) = [x^n] Product_{k>=1} ((1 - x^k)/(1 + x^k))^sigma_n(k).

1, -2, -8, -22, 294, 24982, 1372372, 10145326, -38651841784, -21995644478504, -5088041946350856, 29713279339187796814, 155715351422115081062330, 370606511915720675179342334, -12360092915168107023209454901320

Offset

0,2

Links

Seiichi Manyama, Table of n, a(n) for n = 0..80

Mathematica

Table[SeriesCoefficient[Product[((1 - x^k)/(1 + x^k))^DivisorSigma[n, k], {k, 1, n}], {x, 0, n}], {n, 0, 15}] (* Vaclav Kotesovec, Oct 27 2018 *)

Prog

(PARI) {a(n) = polcoeff(prod(k=1, n, ((1-x^k+x*O(x^n))/(1+x^k+x*O(x^n)))^sigma(k, n)), n)}

Crossrefs

Cf. A320908, A320971, A320972, A321042, A321057.

Sequence in context: A151356 A238530 A303287 * A158466 A065694 A178129

Adjacent sequences: A321065 A321066 A321067 * A321069 A321070 A321071

Keyword

sign

Author

Seiichi Manyama, Oct 26 2018

Status

approved