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A140989 Half the number of n X n binary matrices, symmetric about both diagonal and antidiagonal, having equal row sums. 0
1, 2, 3, 12, 19, 173, 447, 8068, 36753, 1320227, 10915053, 783176689, 11979427593, 1712476502823, 48833478632641, 13961837241242892, 750837577374124089 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..17.

CROSSREFS

Sequence in context: A100570 A056700 A299547 * A281086 A130089 A323119

Adjacent sequences:  A140986 A140987 A140988 * A140990 A140991 A140992

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jul 28 2008

STATUS

approved

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Last modified October 13 18:14 EDT 2019. Contains 327981 sequences. (Running on oeis4.)