OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..150
FORMULA
E.g.f.: exp(T(x) - T(x)^2/2)^2 where T(x) is e.g.f. for A000169.
a(n) = Sum_{m=1..n} A105599(n,m)*2^m.
a(n) ~ 2*n^(n-2)*exp(1). - Vaclav Kotesovec, Aug 16 2013
MAPLE
T:= -LambertW(-x):
egf:= exp(T-T^2/2)^2:
a:= n-> n! * coeff(series(egf, x, n+1), x, n):
seq(a(n), n=0..30); # Alois P. Heinz, Nov 04 2012
MATHEMATICA
nn=20; t=Sum[n^(n-1)x^n/n!, {n, 1, nn}]; Range[0, nn]!CoefficientList[ Series[Exp[(t-t^2/2)]^2, {x, 0, nn}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Geoffrey Critzer, Nov 04 2012
STATUS
approved