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A191650 Number of n X n symmetric binary matrices with each 1 adjacent to exactly 1 antidiagonally neighboring 1. 2
1, 2, 4, 8, 32, 192, 1728, 25920, 518400, 14515200, 609638400, 36578304000, 3292047360000, 444426393600000, 86663146752000000, 24785659971072000000, 10360405867908096000000, 6299126767688122368000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..51

EXAMPLE

Some solutions for n=5:

..0..0..0..0..0....0..1..0..0..0....0..1..0..0..1....0..1..0..0..0

..0..0..1..0..0....1..0..1..0..0....1..0..1..1..0....1..0..1..0..0

..0..1..0..1..0....0..1..0..1..0....0..1..0..1..0....0..1..0..1..0

..0..0..1..0..0....0..0..1..0..1....0..1..1..0..1....0..0..1..0..0

..0..0..0..0..0....0..0..0..1..0....1..0..0..1..0....0..0..0..0..0

CROSSREFS

Sequence in context: A186340 A228920 A064378 * A036544 A094334 A138744

Adjacent sequences:  A191647 A191648 A191649 * A191651 A191652 A191653

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jun 10 2011

STATUS

approved

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Last modified February 18 12:10 EST 2020. Contains 332018 sequences. (Running on oeis4.)