A177632 - OEIS

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

%S 1,20,1668,359280,158479620,124510818960,158686566550368,

%T 306744815112615960

%N Number of permutations of 3 copies of 1..n avoiding adjacent step pattern up, up, down, up, down, down

%K nonn

%O 1,2

%A _R. H. Hardin_ May 10 2010