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A140422 Half the number of n X n symmetric binary matrices with every 1 adjacent to some 0 horizontally or vertically and every 0 adjacent to some 1 horizontally or vertically. 1
1, 5, 47, 849, 29241, 1901849, 234932757, 55047807551, 24470603864937, 20637055514911557, 33018065501295740951, 100220335496292824426843, 577112450349963078523926227 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Table of n, a(n) for n=2..14.

CROSSREFS

Sequence in context: A247982 A222078 A061572 * A145564 A159480 A196460

Adjacent sequences:  A140419 A140420 A140421 * A140423 A140424 A140425

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jun 18 2008

STATUS

approved

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Last modified May 10 14:44 EDT 2021. Contains 343773 sequences. (Running on oeis4.)