Number of symmetric 4 X 4 matrices of nonnegative integers with every row and column adding to n.

Terms

a(0) =1a(1) =10a(2) =56a(3) =214a(4) =641a(5) =1620a(6) =3616a(7) =7340a(8) =13825a(9) =24510a(10) =41336a(11) =66850a(12) =104321a(13) =157864a(14) =232576a(15) =334680a(16) =471681a(17) =652530a(18) =887800a(19) =1189870a(20) =1573121a(21) =2054140a(22) =2651936a(23) =3388164a(24) =4287361a(25) =5377190a(26) =6688696a(27) =8256570a(28) =10119425a(29) =12320080