A333738 - OEIS

A333738

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.

%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