A217823 - OEIS

%I #12 Aug 06 2023 16:40:56

%S 1,1,9,153,3579,101630,3288871

%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).

%C Is this the same sequence as A361190?

%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, A361190.

%K nonn,more

%O 0,3

%A _N. J. A. Sloane_, Oct 13 2012

%E a(5)-a(6) from _Lars Blomberg_, Mar 09 2018

%E a(0)=1 prepended by _Alois P. Heinz_, Jul 31 2023