A356691 a(n) = n! * Sum_{k=0..n} k^(2*k)/k!.

1, 2, 20, 789, 68692, 10109085, 2237436846, 693885130771, 287026057756824, 152677869816810537, 101526778698168105370, 82519543952519610272391, 80487081730821079456710228, 92779662255769290691336848973, 124775610962828705895908497741878

Offset: 0

Author

Seiichi Manyama, Aug 23 2022

Keywords

• nonn

Crossrefs

Cf. A062206, A277506, A350008, A356689.

Programs

PARI

a(n) = n!*sum(k=0, n, k^(2*k)/k!);

PARI

a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=i*v[i]+i^(2*i)); v;

Formula

a(0) = 1; a(n) = n*a(n-1) + n^(2*n).