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A140879 Half the number of n X n binary matrices, symmetric about the diagonal and under 90 degree rotation, having equal row sums. +0
1
1, 1, 1, 2, 1, 5, 1, 20, 1, 139, 1, 1777, 1, 42295, 1, 1888140, 1, 158903233, 1, 25355226287, 1, 7707419775769, 1 (list; graph; listen)
OFFSET

1,4

CROSSREFS

Sequence in context: A163963 A119763 A092142 this_sequence A006556 A108790 A117941

Adjacent sequences: A140876 A140877 A140878 this_sequence A140880 A140881 A140882

KEYWORD

nonn

AUTHOR

Ron Hardin (rhhardin(AT)att.net), Jul 28 2008

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Last modified December 5 08:23 EST 2009. Contains 170348 sequences.


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