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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.

A319159 Given an equilateral triangular grid with side n, containing n(n+1)/2 points, a(n) is the minimal number of points to be selected, such that any equilateral triangle of points will include at least one of the selection.

Table of values

n a(n)
1 1
2 2
3 4
4 7
5 11
6 16
7 22
8 28
9 35
10 44
11 53
12 63
13 74
14 86

List of values

[1, 2, 4, 7, 11, 16, 22, 28, 35, 44, 53, 63, 74, 86]

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

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