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.

A321956 Number of permutations of 3 indistinguishable copies of 1,...,n such that the first and second copies of j are adjacent and there are exactly j-1 numbers between the second and the third copy of j.

Table of values

n a(n)
0 1
1 1
2 0
3 2
4 4
5 0
6 16
7 40
8 0
9 456
10 1759
11 0
12 34636
13 175198
14 0
15 5494621
16 34043062
17 0

List of values

[1, 1, 0, 2, 4, 0, 16, 40, 0, 456, 1759, 0, 34636, 175198, 0, 5494621, 34043062, 0]

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

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