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A177293
Number of permutations of 3 copies of 1..n with all adjacent differences <= 3 in absolute value.
0
1, 1, 20, 1680, 369600, 37850400, 2626916040, 171548183912, 12520880883034, 920942694050320, 65368388837752640
OFFSET
0,3
COMMENTS
a(n) = (3n)!/6^n for n<=4.
CROSSREFS
Cf. A014606.
Sequence in context: A177623 A177633 A177634 * A266738 A177605 A177606
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 06 2010
EXTENSIONS
a(10) from Alois P. Heinz, Jan 18 2016
STATUS
approved