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

Terms

a(0) =-2a(1) =-2a(2) =6a(3) =28a(4) =70a(5) =138a(6) =238a(7) =376a(8) =558a(9) =790a(10) =1078a(11) =1428a(12) =1846a(13) =2338a(14) =2910a(15) =3568a(16) =4318a(17) =5166a(18) =6118a(19) =7180a(20) =8358a(21) =9658a(22) =11086a(23) =12648a(24) =14350a(25) =16198a(26) =18198a(27) =20356a(28) =22678a(29) =25170