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A145779
Number of n X n binary arrays symmetric under 90-degree rotation with all ones connected only either two adjacent vertically or two adjacent horizontally.
0
1, 1, 1, 4, 8, 17, 58, 224, 939, 4970, 30996, 225413, 1970184, 20575972, 252185309, 3690646219, 64088665934, 1323737025941, 32350145726565, 942783467265088, 32507076170340916, 1335377761740727698, 64933573760903971267
OFFSET
1,4
CROSSREFS
Sequence in context: A335274 A296399 A119471 * A252790 A144178 A075558
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 18 2008
STATUS
approved