a(n) = (n-1)*a(n-1) - a(n-4) with a(0)=0, a(1)=1, a(2)=2, a(3)=1.

A122050

a(n) = (n-1)*a(n-1) - a(n-4) with a(0)=0, a(1)=1, a(2)=2, a(3)=1.

Terms

    a(0) =0a(1) =1a(2) =2a(3) =1a(4) =3a(5) =11a(6) =53a(7) =317a(8) =2216a(9) =17717a(10) =159400a(11) =1593683a(12) =17528297a(13) =210321847a(14) =2734024611a(15) =38274750871a(16) =574103734768

External references