a(n) = exp(-1) * Sum_{k>=0} (k*(k + n))^n / k!.

A340822

a(n) = exp(-1) * Sum_{k>=0} (k*(k + n))^n / k!.

Terms

    a(0) =1a(1) =3a(2) =43a(3) =1211a(4) =54812a(5) =3572775a(6) =313493737a(7) =35368945463

External references