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A177604
Number of permutations of 3 copies of 1..n avoiding adjacent step pattern up, up, down, down.
0
1, 20, 1620, 327120, 132712008, 94893564856, 109367900957424, 190384380100623840, 476405198295293272456, 1648273706805009173782464
OFFSET
1,2
CROSSREFS
Sequence in context: A130040 A331563 A250018 * A177621 A177628 A177626
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 10 2010
EXTENSIONS
a(9)-a(10) from Alois P. Heinz, Nov 02 2013
STATUS
approved