A370700 Expansion of e.g.f. exp(-x^2)/(1-x).
1, 1, 0, 0, 12, 60, 240, 1680, 15120, 136080, 1330560, 14636160, 176299200, 2291889600, 32069157120, 481037356800, 7697116627200, 130850982662400, 2355300044697600, 44750700849254400, 895014687427660800, 18795308435980876800, 413496757432991232000
Offset: 0
Programs
-
PARI
my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(-x^2)/(1-x))) -
PARI
a(n) = n!*sum(k=0, n\2, (-1)^k/k!);
Formula
a(n) = n! * Sum_{k=0..floor(n/2)} (-1)^k/k!.