A007138 - cp's OEIS frontend

A007138 Smallest primitive factor of 10^n - 1. Also smallest prime p such that 1/p has repeating decimal expansion of period n.

n	a(n)
1	3
2	11
3	37
4	101
5	41
6	7
7	239
8	73
9	333667
10	9091
11	21649
12	9901
13	53
14	909091
15	31
16	17
17	2071723
18	19
19	1111111111111111111
20	3541
21	43
22	23
23	11111111111111111111111
24	99990001
25	21401
26	859
27	757
28	29
29	3191
30	211
31	2791
32	353
33	67
34	103
35	71
36	999999000001
37	2028119
38	909090909090909091

[3, 11, 37, 101, 41, 7, 239, 73, 333667, 9091, 21649, 9901, 53, 909091, 31, 17, 2071723, 19, 1111111111111111111, 3541, 43, 23, 11111111111111111111111, 99990001, 21401, 859, 757, 29, 3191, 211, 2791, 353, 67, 103, 71, 999999000001, 2028119, 909090909090909091]

cp's OEIS Frontend

A007138 Smallest primitive factor of 10^n - 1. Also smallest prime p such that 1/p has repeating decimal expansion of period n.

Table of values

List of values