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A177284 Number of permutations of 2 copies of 1..n with all adjacent differences <= 3 in absolute value. 0
1, 1, 6, 90, 2520, 41580, 516180, 6068622, 76331906, 958679970, 11679900408, 138047313960, 1610654864328, 18649754961744 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n) = (2n)!/2^n for n<=4.

LINKS

Table of n, a(n) for n=0..13.

CROSSREFS

Cf. A000680.

Sequence in context: A177592 A177593 A132467 * A266735 A177564 A177565

Adjacent sequences:  A177281 A177282 A177283 * A177285 A177286 A177287

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 06 2010

EXTENSIONS

a(0), a(13) from Alois P. Heinz, Jan 14 2016

STATUS

approved

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Last modified January 20 19:53 EST 2020. Contains 331096 sequences. (Running on oeis4.)