Number of 2 X 2 matrices with all terms in {0,1,...,n} and (sum of terms) = n + 3.

Terms

a(0) =0a(1) =1a(2) =16a(3) =44a(4) =80a(5) =125a(6) =180a(7) =246a(8) =324a(9) =415a(10) =520a(11) =640a(12) =776a(13) =929a(14) =1100a(15) =1290a(16) =1500a(17) =1731a(18) =1984a(19) =2260a(20) =2560a(21) =2885a(22) =3236a(23) =3614a(24) =4020a(25) =4455a(26) =4920a(27) =5416a(28) =5944a(29) =6505