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

Terms

a(0) =1a(1) =2a(2) =2a(3) =0a(4) =-4a(5) =-4a(6) =12a(7) =32a(8) =-40a(9) =-264a(10) =56a(11) =2432a(12) =1872a(13) =-24880a(14) =-47344a(15) =276096a(16) =938912a(17) =-3202528a(18) =-18225120a(19) =36217856a(20) =364270016a(21) =-323869248a(22) =-7609269568a(23) =-808015360a(24) =166595915136a(25) =185180268416