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

Terms

a(0) =0a(1) =1a(2) =2a(3) =1a(4) =3a(5) =1a(6) =11a(7) =2a(8) =65a(9) =3a(10) =518a(11) =-38a(12) =5177a(13) =-936a(14) =62162a(15) =-17345a(16) =871204a(17) =-322337a(18) =13956609a(19) =-6350933a(20) =251541299a(21) =-134624336a(22) =5037176913a(23) =-3078652355a(24) =110952516422a(25) =-75846181078