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A177580
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, up, down, up
0
1, 6, 90, 2432, 104088, 6469450, 551224281, 61682514624, 8774836958792, 1546903370655438
OFFSET
1,2
CROSSREFS
Sequence in context: A221097 A177584 A177558 * A177587 A177585 A177559
KEYWORD
nonn
AUTHOR
R. H. Hardin May 10 2010
STATUS
approved