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

Terms

a(0) =0a(1) =4a(2) =16a(3) =44a(4) =96a(5) =180a(6) =304a(7) =476a(8) =704a(9) =996a(10) =1360a(11) =1804a(12) =2336a(13) =2964a(14) =3696a(15) =4540a(16) =5504a(17) =6596a(18) =7824a(19) =9196a(20) =10720a(21) =12404a(22) =14256a(23) =16284a(24) =18496a(25) =20900a(26) =23504a(27) =26316a(28) =29344a(29) =32596