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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n)=(2n)!/2^n for n<=9

LINKS

Table of n, a(n) for n=1..11.

CROSSREFS

Sequence in context: A177594 A177287 A177288 * A177290 A000680 A013297

Adjacent sequences:  A177286 A177287 A177288 * A177290 A177291 A177292

KEYWORD

nonn

AUTHOR

R. H. Hardin May 06 2010

STATUS

approved

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Last modified February 19 11:04 EST 2018. Contains 299330 sequences. (Running on oeis4.)