A177565 - OEIS

%I #3 Mar 31 2012 12:35:44

%S 1,6,90,2520,112920,7398873,667165914,79232435816,11987084051880,

%T 2250732641346600

%N Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, down, down

%K nonn

%O 1,2

%A _R. H. Hardin_ May 10 2010