A177286 - OEIS

%I #3 Mar 31 2012 12:35:42

%S 1,6,90,2520,113400,7484400,349272000,12629539440,394462558980,

%T 11673071453460,348672825749478

%N Number of permutations of 2 copies of 1..n with all adjacent differences <= 5 in absolute value.

%C a(n)=(2n)!/2^n for n<=6

%K nonn

%O 1,2

%A _R. H. Hardin_ May 06 2010