a(0)=0, a(1)=1; for n>1, a(n) = n*a(n-1) - 3*a(n-2).

A303224

a(0)=0, a(1)=1; for n>1, a(n) = n*a(n-1) - 3*a(n-2).

Terms

    a(0) =0a(1) =1a(2) =2a(3) =3a(4) =6a(5) =21a(6) =108a(7) =693a(8) =5220a(9) =44901a(10) =433350a(11) =4632147a(12) =54285714a(13) =691817841a(14) =9522592632a(15) =140763435957

External references