a(n+1) = a(n) - n (if n is odd), a(n+1) = a(n) * n (if n is even).

Terms

a(0) =1a(1) =0a(2) =0a(3) =-3a(4) =-12a(5) =-17a(6) =-102a(7) =-109a(8) =-872a(9) =-881a(10) =-8810a(11) =-8821a(12) =-105852a(13) =-105865a(14) =-1482110a(15) =-1482125a(16) =-23714000a(17) =-23714017a(18) =-426852306a(19) =-426852325a(20) =-8537046500a(21) =-8537046521a(22) =-187815023462a(23) =-187815023485