A380020 Expansion of e.g.f. 1/sqrt(exp(-2*x) - 2*x*exp(-x)).
1, 2, 8, 55, 540, 6861, 106828, 1968443, 41884496, 1010558161, 27259824996, 812935829355, 26556802948624, 943118750625377, 36176486632451012, 1490585029223430691, 65656827447552549504, 3078782615385684631809, 153127047650469476373316
Offset: 0
Keywords
Programs
-
PARI
a(n) = n!*sum(k=0, n, (-2)^k*(k+1)^(n-k)*binomial(-1/2, k)/(n-k)!);
Formula
a(n) = n! * Sum_{k=0..n} (-2)^k * (k+1)^(n-k) * binomial(-1/2,k)/(n-k)!.