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Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to 5 up to permutations of rows and columns.
1

%I #4 Apr 09 2020 12:28:39

%S 1,1,3,13,74,556,5369,64000,917235,15450781,300882997,6682784998,

%T 167423745058,4687321410460,145487540598936,4972006889998672,

%U 185965612590706251,7572297055379416985,334097417273761302271,15905277840810391655517,813931037149014145154401

%N Number of non-isomorphic n X n nonnegative integer symmetric matrices with all row and column sums equal to 5 up to permutations of rows and columns.

%F The a(2) = 3 matrices are:

%F [0 5] [1 4] [2 3]

%F [5 0] [4 1] [3 2]

%Y Column k=5 of A333737.

%K nonn

%O 0,3

%A _Andrew Howroyd_, Apr 08 2020