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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.

A243142 Number of inequivalent (mod D_3) ways to place 3 points on a triangular grid of side n so that they are not vertices of an equilateral triangle of any orientation.

Table of values

n a(n)
2 0
3 3
4 19
5 75
6 218
7 542
8 1178
9 2350
10 4340
11 7585
12 12605
13 20153
14 31094
15 46620
16 68068
17 97212
18 136008
19 186975
20 252855
21 337095
22 443410
23 576378
24 740894
25 942890
26 1188668
27 1485757
28 1842113
29 2267125
30 2770670
31 3364280
32 4060040
33 4871928
34 5814544
35 6904635
36 8159643
37 9599427

List of values

[0, 3, 19, 75, 218, 542, 1178, 2350, 4340, 7585, 12605, 20153, 31094, 46620, 68068, 97212, 136008, 186975, 252855, 337095, 443410, 576378, 740894, 942890, 1188668, 1485757, 1842113, 2267125, 2770670, 3364280, 4060040, 4871928, 5814544, 6904635, 8159643, 9599427]

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

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