OFFSET
0,3
COMMENTS
Stirling transform of A028342.
LINKS
N. J. A. Sloane, Transforms
Eric Weisstein's World of Mathematics, Stirling Transform
FORMULA
E.g.f.: exp( Sum_{k>=1} d(k) * (exp(x) - 1)^k / k ), where d(n) is the number of divisors of n.
a(n) = Sum_{k=0..n} Stirling2(n,k) * A028342(k).
MATHEMATICA
max = 19; Range[0, max]! * CoefficientList[Series[Product[1/(1 - (Exp[x] - 1)^k)^(1/k), {k, 1, max}], {x, 0, max}], x] (* Amiram Eldar, Jun 26 2021 *)
PROG
(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(1/prod(k=1, N, (1-(exp(x)-1)^k)^(1/k))))
(PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(exp(sum(k=1, N, numdiv(k)*(exp(x)-1)^k/k))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jun 26 2021
STATUS
approved