Number of 3 X 3 0..n symmetric arrays with all rows summing to floor(n*3/2).

Terms

a(0) =4a(1) =13a(2) =29a(3) =57a(4) =96a(5) =153a(6) =226a(7) =323a(8) =440a(9) =587a(10) =759a(11) =967a(12) =1204a(13) =1483a(14) =1796a(15) =2157a(16) =2556a(17) =3009a(18) =3505a(19) =4061a(20) =4664a(21) =5333a(22) =6054a(23) =6847a(24) =7696a(25) =8623a(26) =9611a(27) =10683a(28) =11820a(29) =13047