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

Terms

a(0) =1a(1) =1a(2) =-1a(3) =-3a(4) =-7a(5) =-35a(6) =-41a(7) =-287a(8) =-295a(9) =-2655a(10) =-2665a(11) =-29315a(12) =-29327a(13) =-381251a(14) =-381265a(15) =-5718975a(16) =-5718991a(17) =-97222847a(18) =-97222865a(19) =-1847234435a(20) =-1847234455a(21) =-38791923555a(22) =-38791923577a(23) =-892214242271a(24) =-892214242295