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A177557
Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up.
0
1, 5, 55, 1062, 31147, 1313796, 75373533, 5661748406, 539467979009, 63618193828712, 9098617148960622, 1551945898935373561, 311275951583298747596, 72535753321856685723563
OFFSET
1,2
CROSSREFS
Sequence in context: A130031 A336289 A119399 * A158690 A280573 A192723
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 10 2010
EXTENSIONS
a(11)-a(14) from Alois P. Heinz, Nov 02 2013
STATUS
approved