A319361 a(n) = [x^n] exp(Sum_{k>=1} sigma_n(k)*x^k/k).

1, 1, 3, 14, 136, 2411, 88903, 6309849, 866470849, 240522266760, 132000248840652, 141226630324344532, 306101744973083495408, 1327520858367342045830198, 11328405846086223895036194126, 196814026990537767059856457640779, 6894163531963490274906095710739747873

Offset

0,3

Links

Table of n, a(n) for n=0..16.

Formula

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

Mathematica

Table[SeriesCoefficient[Exp[Sum[DivisorSigma[n, k] x^k/k, {k, 1, n}]], {x, 0, n}], {n, 0, 16}]
Table[SeriesCoefficient[Product[1/(1 - x^k)^(k^(n - 1)), {k, 1, n}], {x, 0, n}], {n, 0, 16}]

Crossrefs

Diagonal of A144048.

Cf. A252782, A305207.

Sequence in context: A365997 A126933 A073550 * A367422 A002966 A075654

Adjacent sequences: A319358 A319359 A319360 * A319362 A319363 A319364

Keyword

nonn

Author

Ilya Gutkovskiy, Sep 17 2018

Status

approved