A177293 - OEIS

%I #9 Jan 18 2016 18:40:35

%S 1,1,20,1680,369600,37850400,2626916040,171548183912,12520880883034,

%T 920942694050320,65368388837752640

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

%C a(n) = (3n)!/6^n for n<=4.

%Y Cf. A014606.

%K nonn

%O 0,3

%A _R. H. Hardin_, May 06 2010

%E a(10) from _Alois P. Heinz_, Jan 18 2016