OFFSET
0,3
COMMENTS
Stirling transform of A006125.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..82
FORMULA
G.f.: Sum_{k>=0} 2^binomial(k,2) * x^k / Product_{j=1..k} (1 - j*x).
E.g.f.: Sum_{k>=0} 2^binomial(k,2) * (exp(x) - 1)^k / k!.
a(n) ~ 2^(n*(n-1)/2). - Vaclav Kotesovec, Jun 05 2020
MAPLE
a:= n-> add(Stirling2(n, k)*2^(k*(k-1)/2), k=0..n):
seq(a(n), n=0..19); # Alois P. Heinz, Jun 05 2020
MATHEMATICA
Table[Sum[StirlingS2[n, k] 2^Binomial[k, 2], {k, 0, n}], {n, 0, 16}]
PROG
(PARI) a(n) = sum(k=0, n, stirling(n, k, 2) * 2^binomial(k, 2)); \\ Michel Marcus, Jun 05 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jun 04 2020
STATUS
approved