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A177559
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down.
0
1, 6, 90, 2448, 105218, 6572088, 562874958, 63344668632, 9067009872984, 1608913338743280, 346665863545391736, 89160540714537206616, 26982910637581823115028, 9492077262717161359915632
OFFSET
1,2
CROSSREFS
Sequence in context: A177580 A177587 A177585 * A177581 A177566 A177586
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 10 2010
EXTENSIONS
a(11)-a(14) from Alois P. Heinz, Nov 02 2013
STATUS
approved