Number of restricted 3 X 3 matrices with row and column sums n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =3a(4) =6a(5) =10a(6) =17a(7) =25a(8) =37a(9) =51a(10) =70a(11) =92a(12) =121a(13) =153a(14) =194a(15) =240a(16) =296a(17) =358a(18) =433a(19) =515a(20) =612a(21) =718a(22) =841a(23) =975a(24) =1129a(25) =1295a(26) =1484a(27) =1688a(28) =1917a(29) =2163