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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.

A305623 Number of chiral pairs of rows of n colors with exactly 3 different colors.

Table of values

n a(n)
1 0
2 0
3 3
4 18
5 72
6 267
7 885
8 2880
9 9000
10 27915
11 85233
12 259308
13 783972
14 2366007
15 7122405
16 21422160
17 64364400
18 193307955
19 580316313
20 1741791348
21 5226945372
22 15684152847
23 47058746925
24 141189342840
25 423593188200
26 1270831465995
27 3812595048993
28 11437991207388
29 34314376250772
30 102943948309287
31 308833455491445
32 926503630549920
33 2779517334002400
34 8338565015656035
35 25015720816575273
36 75047214375967428

List of values

[0, 0, 3, 18, 72, 267, 885, 2880, 9000, 27915, 85233, 259308, 783972, 2366007, 7122405, 21422160, 64364400, 193307955, 580316313, 1741791348, 5226945372, 15684152847, 47058746925, 141189342840, 423593188200, 1270831465995, 3812595048993, 11437991207388, 34314376250772, 102943948309287, 308833455491445, 926503630549920, 2779517334002400, 8338565015656035, 25015720816575273, 75047214375967428]

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

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