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.

A240440 Number of 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)
1 0
2 0
3 15
4 105
5 420
6 1260
7 3150
8 6930
9 13860
10 25740
11 45045
12 75075
13 120120
14 185640
15 278460
16 406980
17 581400
18 813960
19 1119195
20 1514205
21 2018940
22 2656500
23 3453450
24 4440150
25 5651100
26 7125300
27 8906625
28 11044215
29 13592880
30 16613520
31 20173560
32 24347400
33 29216880

List of values

[0, 0, 15, 105, 420, 1260, 3150, 6930, 13860, 25740, 45045, 75075, 120120, 185640, 278460, 406980, 581400, 813960, 1119195, 1514205, 2018940, 2656500, 3453450, 4440150, 5651100, 7125300, 8906625, 11044215, 13592880, 16613520, 20173560, 24347400, 29216880]

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

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