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%I #6 Jul 17 2026 22:37:13
%S 1,0,2,6,122,3300,244502,35533946,13894204922,11254924831650,
%T 25931152822648922,123129026842442598010,1767099204159492194923140,
%U 50472055186683607738951340430,4642825806461056714820871058427887,807990421462131145735305221452897896990
%N Number of nonnegative integer matrices with a total of n rows and columns with each row sum and column sum nonzero and at most n.
%e The a(2) = 2 matrices are the 1 X 1 matrices whose only value is 1 or 2.
%e The a(3) = 6 matrices are either 1 X 2 or 2 X 1:
%e [1] [1] [2] [1 1] [1 2] [2 1]
%e [1] [2] [1]
%Y Main diagonal of A397926.
%Y Cf. A397923 (up to row and column permutations).
%K nonn,new
%O 0,3
%A _Andrew Howroyd_, Jul 16 2026