OFFSET
0,3
FORMULA
MATHEMATICA
nmax = 21; CoefficientList[Series[Exp[Sum[Ceiling[DivisorSigma[0, k]/2] x^k/k, {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]!
a[n_] := a[n] = If[n == 0, 1, Sum[Ceiling[DivisorSigma[0, k]/2] a[n - k], {k, 1, n}]/n]; Table[n! a[n], {n, 0, 21}]
nmax = 20; CoefficientList[Series[Exp[Sum[-(x^(k*(1 + k))*LerchPhi[x^k, 1, 1 + k] + Log[1 - x^k])/k, {k, 1, nmax}]], {x, 0, nmax}], x] * Range[0, nmax]! (* Vaclav Kotesovec, Oct 06 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Sep 30 2019
STATUS
approved