Number of 4X4 0..n symmetric arrays with all rows summing to 2*n.

Terms

a(0) =18a(1) =169a(2) =880a(3) =3249a(4) =9522a(5) =23753a(6) =52544a(7) =106009a(8) =198770a(9) =351233a(10) =590832a(11) =953625a(12) =1485778a(13) =2245489a(14) =3304704a(15) =4751377a(16) =6691410a(17) =9251257a(18) =12580080a(19) =16852705a(20) =22271986a(21) =29072121a(22) =37521216a(23) =47924969a(24) =60629426a(25) =76025041a(26) =94549616