a(n) = floor(n^4/4).

Terms

a(0) =0a(1) =0a(2) =4a(3) =20a(4) =64a(5) =156a(6) =324a(7) =600a(8) =1024a(9) =1640a(10) =2500a(11) =3660a(12) =5184a(13) =7140a(14) =9604a(15) =12656a(16) =16384a(17) =20880a(18) =26244a(19) =32580a(20) =40000a(21) =48620a(22) =58564a(23) =69960a(24) =82944a(25) =97656a(26) =114244a(27) =132860a(28) =153664a(29) =176820