cp's OEIS Frontend

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.

A253242 Least k>=0 such that n^(2^k)+1 is prime (for even n), or (n^(2^k)+1)/2 is prime (for odd n); -1 if no such k exists.

Table of values

n a(n)
2 0
3 0
4 0
5 0
6 0
7 2
8 -1
9 0
10 0
11 1
12 0
13 0
14 1
15 1
16 0
17 2
18 0
19 1
20 1
21 0
22 0
23 2
24 1
25 0
26 1
27 -1
28 0
29 1
30 0

List of values

[0, 0, 0, 0, 0, 2, -1, 0, 0, 1, 0, 0, 1, 1, 0, 2, 0, 1, 1, 0, 0, 2, 1, 0, 1, -1, 0, 1, 0]