A356691 - OEIS

%I #14 Aug 23 2022 09:41:10

%S 1,2,20,789,68692,10109085,2237436846,693885130771,287026057756824,

%T 152677869816810537,101526778698168105370,82519543952519610272391,

%U 80487081730821079456710228,92779662255769290691336848973,124775610962828705895908497741878

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

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

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

%o (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;

%Y Cf. A062206, A277506, A350008, A356689.

%K nonn

%O 0,2

%A _Seiichi Manyama_, Aug 23 2022