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%I #10 Sep 08 2015 18:25:56
%S 1,1,2,4,9,21,50,121,296,729
%N Number of equivalence classes of permutations avoiding the pattern {231}.
%C It seems that there is no known g.f.
%H J.-L. Baril, T. Mansour, A. Petrossian, <a href="http://jl.baril.u-bourgogne.fr/equival.pdf">Equivalence classes of permutations modulo excedances</a>, Journal of Combinatorics, Volume 5 (2014), Number 4, doi:10.4310/JOC.2014.v5.n4.a4.
%K nonn,more
%O 0,3
%A _N. J. A. Sloane_, Aug 30 2015
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