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.

A151625 Number of permutations of 2 indistinguishable copies of 1..n with exactly 3 adjacent element pairs in decreasing order.

Table of values

n a(n)
1 0
2 0
3 20
4 1168
5 27664
6 450048
7 6030140
8 72338144
9 811888600
10 8742609264
11 91700484132
12 945739871600
13 9647920866016
14 97729381122976
15 985430937715404
16 9906926101717184
17 99407643757824680
18 996242539625306512
19 9976235831375328564
20 99850100363120616144

List of values

[0, 0, 20, 1168, 27664, 450048, 6030140, 72338144, 811888600, 8742609264, 91700484132, 945739871600, 9647920866016, 97729381122976, 985430937715404, 9906926101717184, 99407643757824680, 996242539625306512, 9976235831375328564, 99850100363120616144]

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

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