A085012 - cp's OEIS frontend

A085012 For p = prime(n), a(n) is the smallest prime q such that pq is a base-2 pseudoprime; that is, 2^(pq-1) = 1 mod pq; a(n) is 0 if no such prime exists.

n	a(n)
2	0
3	0
4	0
5	31
6	0
7	257
8	73
9	89
10	113
11	11
12	73
13	61681
14	127
15	178481
16	157
17	233
18	1321
19	20857
20	281
21	19
22	2731
23	13367
24	23
25	193
26	601
27	307
28	6361
29	37
30	29
31	43
32	2731
33	953
34	168749965921
35	593
36	31
37	53
38	2593
39	499
40	101653
41	62020897
42	54001
43	2281
44	97
45	19707683773
46	5347
47	29191

[0, 0, 0, 31, 0, 257, 73, 89, 113, 11, 73, 61681, 127, 178481, 157, 233, 1321, 20857, 281, 19, 2731, 13367, 23, 193, 601, 307, 6361, 37, 29, 43, 2731, 953, 168749965921, 593, 31, 53, 2593, 499, 101653, 62020897, 54001, 2281, 97, 19707683773, 5347, 29191]

cp's OEIS Frontend

A085012 For p = prime(n), a(n) is the smallest prime q such that pq is a base-2 pseudoprime; that is, 2^(pq-1) = 1 mod pq; a(n) is 0 if no such prime exists.

Table of values

List of values