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

Terms

a(0) =0a(1) =1a(2) =2a(3) =1a(4) =1a(5) =-3a(6) =-2a(7) =-7a(8) =13a(9) =5a(10) =62a(11) =-99a(12) =17a(13) =-719a(14) =1106a(15) =-923a(16) =10453a(17) =-16407a(18) =24298a(19) =-183655a(20) =303217a(21) =-621019a(22) =3792662a(23) =-6685359a(24) =16834061a(25) =-90123923a(26) =170597318a(27) =-494141387a(28) =2423695393a(29) =-4929671655