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A145778
Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only either two adjacent vertically or two adjacent horizontally.
0
1, 1, 1, 2, 2, 3, 6, 10, 21, 46, 106, 253, 820, 2128, 8527, 25843, 122734, 425169, 2572337, 9924088, 75407076, 331598798, 3087553649, 15467749658, 179756366268, 1016119110332, 14755861942091, 94597276047265, 1702584089571489
OFFSET
1,4
CROSSREFS
Sequence in context: A070550 A298179 A185084 * A102762 A320783 A049853
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 18 2008
STATUS
approved