a(1) = 1; a(n) = a(n-1)*(2*(n-1)+a(n-1)) for n > 1.

A145386

a(1) = 1; a(n) = a(n-1)*(2*(n-1)+a(n-1)) for n > 1.

Terms

    a(0) =1a(1) =3a(2) =21a(3) =567a(4) =326025a(5) =106295560875

External references