a(n) = (-1)^n*n*(n-2).

Terms

a(0) =1a(1) =0a(2) =-3a(3) =8a(4) =-15a(5) =24a(6) =-35a(7) =48a(8) =-63a(9) =80a(10) =-99a(11) =120a(12) =-143a(13) =168a(14) =-195a(15) =224a(16) =-255a(17) =288a(18) =-323a(19) =360a(20) =-399a(21) =440a(22) =-483a(23) =528a(24) =-575a(25) =624a(26) =-675a(27) =728a(28) =-783a(29) =840