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A140217 Half the number of n X n binary matrices, symmetric under horizontal reflection, having equal row sums. 1

%I #8 Mar 09 2015 04:29:29

%S 1,1,2,9,34,730,4376,905345,10601986,10009765626,200097656252,

%T 2177748514672962,85812416258106784,4142789042980129347156,

%U 289904403212517959978240,175519033940460517461369847809

%N Half the number of n X n binary matrices, symmetric under horizontal reflection, having equal row sums.

%H R. H. Hardin, Jul 28 2008, <a href="/A140217/b140217.txt">Table of n, a(n) for n = 1..25</a>

%K nonn

%O 1,3

%A _R. H. Hardin_, Jul 28 2008

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Last modified May 19 04:28 EDT 2024. Contains 372666 sequences. (Running on oeis4.)