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.

A238904 Smallest k such that 2^k + (2n+1) and (2n+1)*2^k + 1 are both prime, k <= n, or -1 if no such k exists.

Table of values

n a(n)
0 0
1 1
2 1
3 2
4 1
5 1
6 2
7 1
8 -1
9 6
10 1
11 -1
12 2
13 2
14 1
15 -1
16 6
17 1
18 2
19 1
20 1
21 2
22 9
23 -1
24 2
25 1
26 -1
27 4
28 2
29 -1
30 12
31 4
32 1
33 2
34 1
35 3
36 6
37 3
38 -1
39 2
40 1
41 -1
42 4
43 6
44 9
45 8
46 2
47 1
48 2
49 1
50 3
51 -1
52 1
53 -1
54 6
55 1
56 -1
57 12
58 6
59 3
60 12
61 8
62 1
63 2
64 3
65 3
66 4
67 1
68 -1
69 -1
70 3
71 -1
72 -1
73 60
74 3
75 4
76 2
77 1
78 12

List of values

[0, 1, 1, 2, 1, 1, 2, 1, -1, 6, 1, -1, 2, 2, 1, -1, 6, 1, 2, 1, 1, 2, 9, -1, 2, 1, -1, 4, 2, -1, 12, 4, 1, 2, 1, 3, 6, 3, -1, 2, 1, -1, 4, 6, 9, 8, 2, 1, 2, 1, 3, -1, 1, -1, 6, 1, -1, 12, 6, 3, 12, 8, 1, 2, 3, 3, 4, 1, -1, -1, 3, -1, -1, 60, 3, 4, 2, 1, 12]