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A144054 Number of n X n binary arrays, symmetric under horizontal and vertical reflection, with every 1 adjacent to at least one other 1, but at most one 1 adjacent horizontally and at most one 1 adjacent vertically. 0
1, 2, 1, 5, 15, 65, 233, 1687, 8512, 96837, 990941, 16983353, 265775404, 7061955223, 183338740300, 7436406032400, 326859686075965, 20333610181788816, 1471382970077109810, 140578109521427255473, 16886941052098865528443 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..21.

CROSSREFS

Sequence in context: A268295 A063635 A192264 * A144058 A013014 A012905

Adjacent sequences:  A144051 A144052 A144053 * A144055 A144056 A144057

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 08 2008

STATUS

approved

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Last modified October 6 23:36 EDT 2022. Contains 357270 sequences. (Running on oeis4.)