A383433 Number of king permutations on n elements avoiding the mesh pattern (12, {(0,0),(0,2),(1,0),(1,2),(2,1)}).

1, 1, 0, 0, 2, 12, 76, 556, 4592, 42328, 431184, 4812936, 58440200, 767098296, 10826066776, 163496360680, 2631146363384, 44953977477160, 812713132751832, 15501004918724712, 311078390317974872, 6552553451281418472, 144550752700158416920, 3332886257051337065128, 80168754370190239256408

Offset: 0

Author

Dan Li, Apr 27 2025

Keywords

• nonn
• easy

Comments

A permutation p(1)p(2)...p(n) is a king permutation if |p(i+1)-p(i)|>1 for each 0

Examples

			For n = 4 the a(4) = 2 solutions are the two permutations 2413 and 3142.
For n = 5 the a(5) = 12 solutions are these 12 permutations: 13524, 14253, 24153, 25314, 31524, 35142, 35241, 41352, 42513, 42531, 52413, 53142.
		

Links

• Dan Li and Philip B. Zhang, Distributions of mesh patterns of short lengths on king permutations, arXiv:2411.18131 [math.CO], 2024. See Theorem 4.7 at page 21.

Crossrefs

Cf. A002464, A382644, A382645, A382651, A383040, A383107, A383312, A383406, A383407, A383408.

Formula

G.f.: (2*A(t) - t - 1)/(A(t) - t) where A(t)=Sum_{n >= 0} n!*t^n*(1-t)^n/(1+t)^n is the g.f. for king permutations given by A002464.

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