%I #5 Apr 09 2020 12:29:04
%S 1,1,2,5,33,556,31781,5882230,3589936407,7347418294141,
%T 51304793433150418,1240428029662246026001,105148289475978338858008298,
%U 31582581551955332317665959184087
%N Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to n up to permutations of rows and columns.
%e The a(3) = 5 matrices are:
%e [0, 0, 3] [0, 1, 2] [0, 1, 2] [1, 0, 2] [1, 1, 1]
%e [0, 3, 0] [1, 1, 1] [1, 2, 0] [0, 3, 0] [1, 1, 1]
%e [3, 0, 0] [2, 1, 0] [2, 0, 1] [2, 0, 1] [1, 1, 1]
%Y Main diagonal of A333737.
%K nonn,more
%O 0,3
%A _Andrew Howroyd_, Apr 08 2020