A363785 A variant of payphone permutations: given a row of n payphones, a(n) is the number ways for n people to choose the payphones in order, where each person chooses an unoccupied payphone such that the closest occupied payphone is as distant as possible, and a payphone adjacent to a single occupied payphone is preferred over a payphone sandwiched between two occupied payphones.

1, 2, 4, 6, 16, 28, 120, 264, 576, 2784, 11040, 37440, 204672, 679680, 2511360, 15655680, 52945920, 232796160, 2456801280, 11867627520, 97875025920, 576737280000, 4012233523200, 20013325516800, 215802239385600, 1778700504268800, 9687506721177600, 88613303353344000, 448250987623219200

Offset: 1

Author

Max Alekseyev, Jun 21 2023

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..100
• Max A. Alekseyev, Enumeration of Payphone Permutations, arXiv:2304.04324 [math.CO], 2023.

Crossrefs

Cf. A358056, A095236, A095239, A095912, A361294, A361295, A361296, A362192, A363785.