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A140363 Number of n X n symmetric binary matrices with every 1 adjacent horizontally (and vertically) to some other 1. 0
1, 2, 8, 40, 310, 4155, 89670, 3070348, 168002166, 14759284768, 2075629841521, 467015770766284, 168271584258210602, 97113565640564063834, 89738360022163805917690 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..15.

CROSSREFS

Sequence in context: A281910 A180736 A111394 * A280921 A208962 A012597

Adjacent sequences:  A140360 A140361 A140362 * A140364 A140365 A140366

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jun 15 2008

STATUS

approved

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Last modified September 20 12:39 EDT 2020. Contains 337264 sequences. (Running on oeis4.)