%I #8 Oct 08 2018 09:30:38
%S 1,19,642,27453,1339531,71173264
%N Number of permutations of length 3n with descent set {3, 6, ...} that avoid a certain pattern of length 4 or 5 (see Lewis, 2012, Appendix, for precise definition).
%H J. B. Lewis, <a href="https://dspace.mit.edu/handle/1721.1/73444">Pattern Avoidance for Alternating Permutations and Reading Words of Tableaux</a>, Ph. D. Dissertation, Department of Mathematics, MIT, 2012.
%Y Cf. A181197, A217799-A217830.
%K nonn,more
%O 1,2
%A _N. J. A. Sloane_, Oct 13 2012
%E a(5)-a(6) from _Lars Blomberg_, Mar 09 2018