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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.

A331868 Numbers k for which R(k) + 4*10^floor(k/2-1) is prime, where R(n) = (10^n-1)/9 (repunit: A002275).

Table of values

n	a(n)
1	4
2	147
3	270
4	1288
5	1551
6	3427

List of values

[4, 147, 270, 1288, 1551, 3427]

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