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A177289
Number of permutations of 2 copies of 1..n with all adjacent differences <= 8 in absolute value.
0
1, 6, 90, 2520, 113400, 7484400, 681080400, 81729648000, 12504636144000, 1522786801536000, 152883132197796000
OFFSET
1,2
COMMENTS
a(n)=(2n)!/2^n for n<=9
CROSSREFS
Sequence in context: A177594 A177287 A177288 * A177290 A000680 A013297
KEYWORD
nonn
AUTHOR
R. H. Hardin May 06 2010
STATUS
approved