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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.

A155850 a(n) = smallest k > 1 such that k-1 and k+1 together have n prime divisors.

Table of values

n a(n)
1 2
2 4
3 3
4 5
5 7
6 15
7 17
8 31
9 65
10 129
11 127
12 449
13 511
14 2561
15 1025
16 7937
17 12799
18 20481
19 8191
20 28673
21 65537
22 131071
23 458751
24 360449
25 966655
26 524287
27 4194303
28 2097151
29 29360129
30 34865153
31 67108865
32 134217729
33 33554431
34 608174081
35 268435457
36 536870911
37 4831838207

List of values

[2, 4, 3, 5, 7, 15, 17, 31, 65, 129, 127, 449, 511, 2561, 1025, 7937, 12799, 20481, 8191, 28673, 65537, 131071, 458751, 360449, 966655, 524287, 4194303, 2097151, 29360129, 34865153, 67108865, 134217729, 33554431, 608174081, 268435457, 536870911, 4831838207]

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

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