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%I #46 May 24 2018 15:54:56
%S 1,3,11,35,132,471,1806,7042,28494,118662,510517,2262738,10337474,
%T 48625631,235357470,1171163995,5986424739,31403695142,168913667164,
%U 930739116386,5249162406890,30275048671498,178428441191289,1073737691984694,6592909590432719
%N Number of nonisomorphic binary n X n matrices with two 1's per column under row and column permutations.
%H Andrew Howroyd, <a href="/A247417/b247417.txt">Table of n, a(n) for n = 2..50</a>
%H Marko Riedel, <a href="/A247417/a247417.maple.txt">MAPLE Cycle Indices and Burnside Computation for Non-Isomorphic N by N binary matrices with K entries per column under row and column permutation</a>
%H StackExchange, <a href="http://math.stackexchange.com/questions/616834/">How many arrays with crossed cells, order of rows/columns irrelevant</a>, Dec 13 2013
%p Using the uploaded program the call is seq(matrix_marks(n,2), n=3..15);
%o (PARI) \\ See A304942 for Blocks
%o a(n) = Blocks(n, n, 2); \\ _Andrew Howroyd_, May 24 2018
%Y Column k=2 of A304942.
%Y Cf. A247596, A247597, A247598.
%K nonn
%O 2,2
%A _Marko Riedel_, Sep 21 2014
%E Terms a(17) and beyond from _Andrew Howroyd_, May 23 2018
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