A097406 - cp's OEIS frontend

A097406 Largest primitive prime factor of 2^n-1, or a(n) = 1 if no such prime exists.

n	a(n)
1	1
2	3
3	7
4	5
5	31
6	1
7	127
8	17
9	73
10	11
11	89
12	13
13	8191
14	43
15	151
16	257
17	131071
18	19
19	524287
20	41
21	337
22	683
23	178481
24	241
25	1801
26	2731
27	262657
28	113
29	2089
30	331
31	2147483647
32	65537
33	599479
34	43691
35	122921
36	109
37	616318177
38	174763
39	121369
40	61681
41	164511353
42	5419

[1, 3, 7, 5, 31, 1, 127, 17, 73, 11, 89, 13, 8191, 43, 151, 257, 131071, 19, 524287, 41, 337, 683, 178481, 241, 1801, 2731, 262657, 113, 2089, 331, 2147483647, 65537, 599479, 43691, 122921, 109, 616318177, 174763, 121369, 61681, 164511353, 5419]

cp's OEIS Frontend

A097406 Largest primitive prime factor of 2^n-1, or a(n) = 1 if no such prime exists.

Table of values

List of values