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A177294
Number of permutations of 3 copies of 1..n with all adjacent differences <= 4 in absolute value.
0
1, 1, 20, 1680, 369600, 168168000, 41494252800, 6923871998400, 983114244363720, 139528504017728552
OFFSET
0,3
COMMENTS
a(n) = (3n)!/6^n for n<=5.
CROSSREFS
Cf. A014606.
Sequence in context: A177617 A177629 A177630 * A177615 A177616 A177295
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 06 2010
STATUS
approved