Number of 3 X 3 matrices with unit determinant and nonnegative integer entries whose sum is n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =3a(4) =18a(5) =54a(6) =126a(7) =261a(8) =432a(9) =783a(10) =1134a(11) =1899a(12) =2286a(13) =3960a(14) =4680a(15) =6876a(16) =8262a(17) =12654a(18) =12618a(19) =20799a(20) =20934a(21) =30024a(22) =32760a(23) =48141a(24) =43632a(25) =68976a(26) =68094a(27) =91161a(28) =93042a(29) =138006