a(n) = 2*(n^3 + n^2 + n - 1).

Terms

a(0) =-2a(1) =4a(2) =26a(3) =76a(4) =166a(5) =308a(6) =514a(7) =796a(8) =1166a(9) =1636a(10) =2218a(11) =2924a(12) =3766a(13) =4756a(14) =5906a(15) =7228a(16) =8734a(17) =10436a(18) =12346a(19) =14476a(20) =16838a(21) =19444a(22) =22306a(23) =25436a(24) =28846a(25) =32548a(26) =36554a(27) =40876a(28) =45526a(29) =50516