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%I #10 May 10 2013 12:44:33
%S 1,3,18,92,458,1982,7928,28592,95138,292993,845027,2295322,5915631,
%T 14535676,34224682,77510148,169459010,358698558,737106306,1473867060,
%U 2873564862,5472731212,10198198452,18621343624,33361303957,58713103696
%N Number of 4 X n nonnegative integer matrices with all column sums 3, up to row and column permutation.
%H Vladeta Jovovic, <a href="/A058407/a058407.pdf">Number of m x l nonnegative integer matrices with all column sums equal to n, up to row and column permutation</a>
%F G.f.: 1 / 24*(1 / (1 - x)^20 + 6 / (1 - x)^6 / (1 - x^2)^7 + 3 / (1 - x^2)^10 + 8 / (1 - x)^2 / (1 - x^3)^6 + 6 / (1 - x^4)^5).
%Y Cf. A050532, A058390, A058407, A058408, A058410.
%K easy,nonn
%O 0,2
%A _Vladeta Jovovic_, Nov 25 2000
%E More terms from _Max Alekseyev_, Jun 21 2011
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