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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.

A291301 a(n) = prime that is eventually reached when x -> sigma(x)-1 is repeatedly applied to the product of the first n primes, or -1 if no prime is ever reached.

Table of values

n a(n)
1 2
2 11
3 71
4 743
5 6911
6 117239
7 2013983
8 34836479
9 921086711
10 33596203871
11 18754852859999
12 1306753691335679
13 2795529813471359
14 200489563747397471
15 7143750592470475271
16 146095655504943513599
17 161739770170976834876927
18 543475838478389870591999
19 317180662337566737324195839

List of values

[2, 11, 71, 743, 6911, 117239, 2013983, 34836479, 921086711, 33596203871, 18754852859999, 1306753691335679, 2795529813471359, 200489563747397471, 7143750592470475271, 146095655504943513599, 161739770170976834876927, 543475838478389870591999, 317180662337566737324195839]

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

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