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A177565
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, down
0
1, 6, 90, 2520, 112920, 7398873, 667165914, 79232435816, 11987084051880, 2250732641346600
OFFSET
1,2
CROSSREFS
Sequence in context: A177284 A266735 A177564 * A177576 A177588 A177589
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved