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%I #5 Oct 22 2013 18:43:45
%S 1,26,2506,624446,322530466,301458657626,465560613932206,
%T 1112284734271280846
%N Number of permutations of 4 copies of 1..n avoiding adjacent step pattern up, down.
%K nonn
%O 1,2
%A _R. H. Hardin_, May 10 2010
%E a(8) from _Alois P. Heinz_, Oct 22 2013