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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
OFFSET
1,2
CROSSREFS
Sequence in context: A268295 A063635 A192264 * A144058 A013014 A012905
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 08 2008
STATUS
approved