a(n) = 4*n*(2*n + 1).

Terms

a(0) =0a(1) =12a(2) =40a(3) =84a(4) =144a(5) =220a(6) =312a(7) =420a(8) =544a(9) =684a(10) =840a(11) =1012a(12) =1200a(13) =1404a(14) =1624a(15) =1860a(16) =2112a(17) =2380a(18) =2664a(19) =2964a(20) =3280a(21) =3612a(22) =3960a(23) =4324a(24) =4704a(25) =5100a(26) =5512a(27) =5940a(28) =6384a(29) =6844