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%I #8 Jan 16 2020 01:12:53
%S 1,2,15,317,12586,803764,75603729,9880078404,1719511013708,
%T 385900586669488,108870763685147631,37821200661333033093,
%U 15903952714275755480410,7978911737260660423782839,4717171385049289138016854041,3251403192784472823846341645000
%N Number of nonnegative integer matrices with n distinct columns and any number of distinct nonzero rows with each column sum being 3 and rows in decreasing lexicographic order.
%C The condition that the rows be in decreasing order is equivalent to considering nonequivalent matrices with distinct rows up to permutation of rows.
%H Andrew Howroyd, <a href="/A331344/b331344.txt">Table of n, a(n) for n = 0..100</a>
%Y Row n=3 of A331160.
%Y Cf. A331196, A331316,
%K nonn
%O 0,2
%A _Andrew Howroyd_, Jan 14 2020