cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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.

Table of values

n a(n)
1 1
2 2
3 4
4 6
5 16
6 28
7 120
8 264
9 576
10 2784
11 11040
12 37440
13 204672
14 679680
15 2511360
16 15655680
17 52945920
18 232796160
19 2456801280
20 11867627520
21 97875025920
22 576737280000
23 4012233523200
24 20013325516800
25 215802239385600
26 1778700504268800
27 9687506721177600
28 88613303353344000
29 448250987623219200

List of values

[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]