Number of 2 X 2 matrices with all terms in {0,1,...,n} and (sum of terms) = n + 4.

Terms

a(0) =0a(1) =0a(2) =10a(3) =40a(4) =85a(5) =140a(6) =206a(7) =284a(8) =375a(9) =480a(10) =600a(11) =736a(12) =889a(13) =1060a(14) =1250a(15) =1460a(16) =1691a(17) =1944a(18) =2220a(19) =2520a(20) =2845a(21) =3196a(22) =3574a(23) =3980a(24) =4415a(25) =4880a(26) =5376a(27) =5904a(28) =6465a(29) =7060