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

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =8a(6) =10a(7) =36a(8) =21a(9) =216a(10) =-126a(11) =1960a(12) =-3751a(13) =25044a(14) =-74230a(15) =403144a(16) =-1489095a(17) =7638000a(18) =-32168046a(19) =164287728a(20) =-756314855a(21) =3929115500a(22) =-19332654222a(23) =103079467832a(24) =-535020703583