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Number of permutations of 3 copies of 1..n avoiding adjacent step pattern up, down, down, up.
0

%I #6 Nov 02 2013 20:43:58

%S 1,20,1477,263978,93489715,57920130894,57577729726875,

%T 86198179666698834,185132216218421052414,548986840452318863546904

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

%K nonn

%O 1,2

%A _R. H. Hardin_, May 10 2010

%E a(9)-a(10) from _Alois P. Heinz_, Nov 02 2013