A361295 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 among the available payphones adjacent to a single occupied payphone the most preferred are payphones at open ends.

1, 2, 4, 6, 12, 40, 144, 384, 1008, 6816, 33600, 115200, 783360, 3024000, 16450560, 140636160, 558351360, 2262435840, 29599395840, 180278784000, 2124328550400, 13664957644800, 127667338444800, 852837440716800, 11377123378790400, 116737211695104000, 816490952589312000

Offset: 1

Author

Max Alekseyev, Apr 08 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, A361296, A362192, A363785.

Extensions

Definition corrected by Max Alekseyev, Jun 21 2023