a(n) = floor(n^4/64).

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =4a(5) =9a(6) =20a(7) =37a(8) =64a(9) =102a(10) =156a(11) =228a(12) =324a(13) =446a(14) =600a(15) =791a(16) =1024a(17) =1305a(18) =1640a(19) =2036a(20) =2500a(21) =3038a(22) =3660a(23) =4372a(24) =5184a(25) =6103a(26) =7140a(27) =8303a(28) =9604a(29) =11051