a(n) = Sum_{k=0..n} (k!)^2 * Stirling_2(n,k)^2.

A048144

a(n) = Sum_{k=0..n} (k!)^2 * Stirling_2(n,k)^2.

Terms

    a(0) =1a(1) =1a(2) =5a(3) =73a(4) =2069a(5) =95401a(6) =6487445a(7) =610093513a(8) =75796724309

External references