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Number of n X n nonnegative integer symmetric matrices with all row and column sums equal to n.
1

%I #4 Apr 09 2020 12:30:38

%S 1,1,3,23,641,62781,22393101,29445929253,144413237202513,

%T 2664174112921403401,186127457781265060985293,

%U 49509854244685925218197355989,50364892612276937755557718571828543,196663809308382999799947201118326883990475

%N Number of n X n nonnegative integer symmetric matrices with all row and column sums equal to n.

%Y Main diagonal of A188403.

%K nonn

%O 0,3

%A _Andrew Howroyd_, Apr 08 2020