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A140984 Half the number of n X n binary matrices, symmetric under 180 degree rotation, having equal row sums. 1
1, 2, 4, 35, 226, 7592, 156752, 22458249, 1718157826, 941605438142, 250228936146872, 572800408273738658, 580834777459374862880, 5136409738603278958315040, 18792196647668946085817284928 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Jul 28 2008, Table of n, a(n) for n = 1..25

CROSSREFS

Sequence in context: A236399 A132529 A027681 * A057996 A009090 A009295

Adjacent sequences:  A140981 A140982 A140983 * A140985 A140986 A140987

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jul 28 2008

STATUS

approved

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Last modified July 12 10:20 EDT 2020. Contains 335657 sequences. (Running on oeis4.)