Number of n X 3 0..2 matrices with row sums 3 and column sums n up to permutations of rows.

Terms

a(0) =1a(1) =1a(2) =4a(3) =6a(4) =12a(5) =18a(6) =30a(7) =42a(8) =63a(9) =85a(10) =118a(11) =154a(12) =204a(13) =258a(14) =330a(15) =408a(16) =507a(17) =615a(18) =748a(19) =892a(20) =1066a(21) =1254a(22) =1476a(23) =1716a(24) =1995a(25) =2295a(26) =2640a(27) =3010a(28) =3430a(29) =3880