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%I #11 Feb 09 2020 14:26:02
%S 1,3,21,162,1636,19977,298416,5300296,110219750,2639842989,
%T 71859429837,2198244062193,74860247277672,2815351714711122,
%U 116130005180284423,5222901881792429337,254791333526874348652,13420798291405599027605,760201936044714899316798,46137860613934391781325337,2990483661567310913388458734
%N Number of n-rowed matrices with entries {0,1,2,3} and all row sums 3, up to row and column permutation.
%o (PARI) \\ See A318951 for RowSumMats
%o a(n)=RowSumMats(n, 3*n, 3); \\ _Andrew Howroyd_, Sep 06 2018
%Y Row n=3 of A331485.
%Y Cf. A007717, A058407, A058409, A050913.
%K nonn
%O 0,2
%A _Vladeta Jovovic_, Nov 27 2000
%E a(11)-a(20) from _Andrew Howroyd_, Sep 06 2018