a(n) = n!*A001515(n-1) with a(0) = 1.

A143990

a(n) = n!*A001515(n-1) with a(0) = 1.

Terms

    a(0) =1a(1) =1a(2) =4a(3) =42a(4) =888a(5) =31920a(6) =1750320a(7) =136115280a(8) =14254007040

External references