%I
%S 1,4,29,292,3620,51866,827415,14350467,266218320
%N Number of alternating permutations on 2n letters that avoid a certain pattern of length 4 (see Lewis, 2012, Appendix, for precise definition).
%H Andrew R. Conway, Anthony J. Guttmann, Paul ZinnJustin, <a href="https://arxiv.org/abs/1709.01248">1324avoiding permutations revisited</a> arXiv:1709.01248 [math.CO], 2017.
%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, A217799A217830.
%K nonn,more
%O 1,2
%A _N. J. A. Sloane_, Oct 12 2012
%E a(7)a(9) from _Lars Blomberg_, Feb 17 2018
