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A145791
Number of n X n binary arrays symmetric under horizontal and vertical reflection with all ones connected only either four adjacent vertically or four adjacent horizontally.
0
1, 1, 1, 3, 1, 6, 1, 17, 26, 113, 318, 1310, 4072, 21570, 65328, 442636, 1558383, 13750703, 69409037, 646392443, 4686057331, 48049954607, 457665821401, 5254108049909, 63960030819910, 855193502729867
OFFSET
1,4
CROSSREFS
Sequence in context: A165552 A067231 A218971 * A348661 A322041 A130302
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 19 2008
STATUS
approved