A177294 - OEIS

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A177294

Number of permutations of 3 copies of 1..n with all adjacent differences <= 4 in absolute value.

%I #6 Jan 18 2016 18:32:37

%S 1,1,20,1680,369600,168168000,41494252800,6923871998400,

%T 983114244363720,139528504017728552

%N Number of permutations of 3 copies of 1..n with all adjacent differences <= 4 in absolute value.

%C a(n) = (3n)!/6^n for n<=5.

%Y Cf. A014606.

%K nonn

%O 0,3

%A _R. H. Hardin_, May 06 2010