A283461 - cp's OEIS frontend

A283461 Second-largest prime factor of 2^n - 1, if composite, or 1 otherwise.

n	a(n)
2	1
3	1
4	3
5	1
6	3
7	1
8	5
9	7
10	11
11	23
12	7
13	1
14	43
15	31
16	17
17	1
18	19
19	1
20	31
21	127
22	89
23	47
24	17
25	601
26	2731
27	73
28	113
29	1103
30	151
31	1
32	257
33	89
34	43691
35	127
36	73
37	223
38	174763
39	8191
40	41
41	13367
42	337
43	9719
44	683
45	631
46	178481
47	4513
48	257
49	127
50	1801
51	11119
52	2731

[1, 1, 3, 1, 3, 1, 5, 7, 11, 23, 7, 1, 43, 31, 17, 1, 19, 1, 31, 127, 89, 47, 17, 601, 2731, 73, 113, 1103, 151, 1, 257, 89, 43691, 127, 73, 223, 174763, 8191, 41, 13367, 337, 9719, 683, 631, 178481, 4513, 257, 127, 1801, 11119, 2731]

cp's OEIS Frontend

A283461 Second-largest prime factor of 2^n - 1, if composite, or 1 otherwise.

Table of values

List of values