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A191506 Number of n X n symmetric binary matrices with each 1 adjacent to no more than 1 horizontally or vertically neighboring 1 1
2, 5, 25, 195, 2475, 53324, 1872113, 109037035, 10508450377, 1672058437225, 440124911303718, 191498508664286039, 137739615464486164780, 163796811382099494131871, 322006666961136384120723488 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
Some solutions for n=4
..1..0..1..0....0..0..0..1....0..1..0..0....0..0..0..1....1..0..0..1
..0..1..0..1....0..0..0..1....1..0..0..0....0..0..1..0....0..1..0..0
..1..0..1..0....0..0..1..0....0..0..1..0....0..1..0..0....0..0..0..1
..0..1..0..1....1..1..0..1....0..0..0..1....1..0..0..1....1..0..1..0
CROSSREFS
Sequence in context: A268120 A324263 A049650 * A139007 A015486 A191951
KEYWORD
nonn
AUTHOR
R. H. Hardin Jun 04 2011
STATUS
approved

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Last modified March 19 01:57 EDT 2024. Contains 370952 sequences. (Running on oeis4.)