a(n) = 4*n^3 - 3*n^2 + 2*n - 1.

Terms

a(0) =2a(1) =23a(2) =86a(3) =215a(4) =434a(5) =767a(6) =1238a(7) =1871a(8) =2690a(9) =3719a(10) =4982a(11) =6503a(12) =8306a(13) =10415a(14) =12854a(15) =15647a(16) =18818a(17) =22391a(18) =26390a(19) =30839a(20) =35762a(21) =41183a(22) =47126a(23) =53615a(24) =60674a(25) =68327a(26) =76598a(27) =85511a(28) =95090a(29) =105359