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

Terms

a(0) =0a(1) =1a(2) =-1a(3) =-1a(4) =0a(5) =-1a(6) =5a(7) =-5a(8) =16a(9) =-55a(10) =35a(11) =-1045a(12) =64a(13) =-30305a(14) =105a(15) =-1242505a(16) =160a(17) =-68337775a(18) =231a(19) =-4851982025a(20) =320a(21) =-431826400225a(22) =429a(24) =560a(26) =715a(28) =896