A321057 - OEIS

%I #21 Oct 28 2018 10:47:04

%S 1,2,12,94,1522,48154,3087600,377880794,93356591804,46415548879976,

%T 44773963087975388,86770399797767582434,340765670578000502365102,

%U 2625605734866823121935402410,40755373130582885082115865730892,1290109927277547765958474680645604818

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

%H Seiichi Manyama, <a href="/A321057/b321057.txt">Table of n, a(n) for n = 0..80</a>

%t 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 *)

%o (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)}

%Y Cf. A301554, A301555, A301556, A319647, A321042, A321068.

%K nonn

%O 0,2

%A _Seiichi Manyama_, Oct 26 2018