a(n) = n*a(n-1) - a(n-2) with a(0) = 0, a(1) = 1.

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =18a(5) =85a(6) =492a(7) =3359a(8) =26380a(9) =234061a(10) =2314230a(11) =25222469a(12) =300355398a(13) =3879397705a(14) =54011212472a(15) =806288789375