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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.

A281627 a(n) is the smallest number k such that sigma(phi(k)) = A062402(k) is the n-th Mersenne prime (A000668(n)), or 0 if no such k exists.

Table of values

n a(n)
1 3
2 5
3 17
4 85
5 4369
6 65537
7 327685
8 1431655765
9 2305843009213693952
10 618970019642690137449562112
11 162259276829213363391578010288128
12 170141183460469231731687303715884105728

List of values

[3, 5, 17, 85, 4369, 65537, 327685, 1431655765, 2305843009213693952, 618970019642690137449562112, 162259276829213363391578010288128, 170141183460469231731687303715884105728]

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

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