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A141512
Number of n X n binary matrices, symmetric about the diagonal and under 90-degree rotation, with no more than 3 ones in any 2 X 2 subblock.
1
1, 2, 1, 7, 4, 49, 21, 648, 245, 16475, 5184, 801489, 214175, 74700792, 16831269, 13333992705, 2539826928, 4558747755857, 733369598775, 2985167883475040, 405728550271273, 3743977846899435969, 429864175220405760
OFFSET
0,2
LINKS
CROSSREFS
Sequence in context: A087059 A120872 A204771 * A143877 A319464 A019642
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 10 2008
STATUS
approved