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A177287
Number of permutations of 2 copies of 1..n with all adjacent differences <= 6 in absolute value.
0
1, 1, 6, 90, 2520, 113400, 7484400, 681080400, 46118872800, 2475822056400, 113874710498640, 4828589411913540
OFFSET
0,3
COMMENTS
a(n) = (2n)!/2^n for n<=7.
CROSSREFS
Sequence in context: A177575 A177286 A177594 * A177288 A177289 A177290
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 06 2010
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Jul 21 2018
STATUS
approved