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%I #6 Nov 02 2013 16:59:53
%S 1,5,55,1062,31147,1313796,75373533,5661748406,539467979009,
%T 63618193828712,9098617148960622,1551945898935373561,
%U 311275951583298747596,72535753321856685723563
%N Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up.
%K nonn
%O 1,2
%A _R. H. Hardin_, May 10 2010
%E a(11)-a(14) from _Alois P. Heinz_, Nov 02 2013
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