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.

A245855 Number of preferential arrangements of n labeled elements such that the minimal number of elements per rank equals 2.

Table of values

n a(n)
2 1
3 0
4 6
5 20
6 120
7 672
8 5516
9 40140
10 368640
11 3521870
12 37445298
13 422339502
14 5215454426
15 68144100780
16 954428684280
17 14160968076584
18 222769496190060
19 3692874342747114
20 64493471050666430
21 1181830474135532130
22 22692074431844298558
23 455404848204906308984

List of values

[1, 0, 6, 20, 120, 672, 5516, 40140, 368640, 3521870, 37445298, 422339502, 5215454426, 68144100780, 954428684280, 14160968076584, 222769496190060, 3692874342747114, 64493471050666430, 1181830474135532130, 22692074431844298558, 455404848204906308984]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.