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A177584
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, down, up, down
0
1, 6, 90, 2350, 99652, 6149364, 520470852, 58016022928, 8228785850728, 1447745572453056
OFFSET
1,2
CROSSREFS
Sequence in context: A001499 A147630 A221097 * A177558 A177580 A177587
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved