A249800 - cp's OEIS frontend

A249800 a(n) is the smallest prime q such that n(q+1)+1 is prime, that is, the smallest prime q such that n = (p-1)/(q+1) with p prime; or a(n) = -1 if no such q exists.

n	a(n)
1	3
2	2
3	3
4	2
5	5
6	2
7	3
8	11
9	3
10	2
11	5
12	2
13	3
14	2
15	3
16	5
17	5
18	3
19	11
20	2
21	5
22	2
23	5
24	2
25	3
26	2
27	3
28	3
29	7
30	5
31	11
32	2
33	5
34	2
35	5
36	2
37	3
38	5
39	3
40	5
41	17
42	2
43	3
44	7
45	3
46	2
47	5
48	3
49	3
50	2
51	5
52	2
53	13
54	2
55	5
56	5
57	3
58	3
59	11
60	2
61	5
62	5
63	5
64	2
65	7
66	2
67	3
68	5
69	3
70	2
71	7
72	5
73	3
74	2
75	7
76	2
77	5
78	3
79	3
80	2
81	5
82	113
83	5
84	3
85	11

[3, 2, 3, 2, 5, 2, 3, 11, 3, 2, 5, 2, 3, 2, 3, 5, 5, 3, 11, 2, 5, 2, 5, 2, 3, 2, 3, 3, 7, 5, 11, 2, 5, 2, 5, 2, 3, 5, 3, 5, 17, 2, 3, 7, 3, 2, 5, 3, 3, 2, 5, 2, 13, 2, 5, 5, 3, 3, 11, 2, 5, 5, 5, 2, 7, 2, 3, 5, 3, 2, 7, 5, 3, 2, 7, 2, 5, 3, 3, 2, 5, 113, 5, 3, 11]

cp's OEIS Frontend

A249800 a(n) is the smallest prime q such that n(q+1)+1 is prime, that is, the smallest prime q such that n = (p-1)/(q+1) with p prime; or a(n) = -1 if no such q exists.

Table of values

List of values

n	a(n)
1	3
2	2
3	3
4	2
5	5
6	2
7	3
8	11
9	3
10	2
11	5
12	2
13	3
14	2
15	3
16	5
17	5
18	3
19	11
20	2
21	5
22	2
23	5
24	2
25	3
26	2
27	3
28	3
29	7
30	5
31	11
32	2
33	5
34	2
35	5
36	2
37	3
38	5
39	3
40	5
41	17
42	2
43	3
44	7
45	3
46	2
47	5
48	3
49	3
50	2
51	5
52	2
53	13
54	2
55	5
56	5
57	3
58	3
59	11
60	2
61	5
62	5
63	5
64	2
65	7
66	2
67	3
68	5
69	3
70	2
71	7
72	5
73	3
74	2
75	7
76	2
77	5
78	3
79	3
80	2
81	5
82	113
83	5
84	3
85	11

n	a(n)
1	3
2	2
3	3
4	2
5	5
6	2
7	3
8	11
9	3
10	2
11	5
12	2
13	3
14	2
15	3
16	5
17	5
18	3
19	11
20	2
21	5
22	2
23	5
24	2
25	3
26	2
27	3
28	3
29	7
30	5
31	11
32	2
33	5
34	2
35	5
36	2
37	3
38	5
39	3
40	5
41	17
42	2
43	3
44	7
45	3
46	2
47	5
48	3
49	3
50	2
51	5
52	2
53	13
54	2
55	5
56	5
57	3
58	3
59	11
60	2
61	5
62	5
63	5
64	2
65	7
66	2
67	3
68	5
69	3
70	2
71	7
72	5
73	3
74	2
75	7
76	2
77	5
78	3
79	3
80	2
81	5
82	113
83	5
84	3
85	11

n	a(n)
1	3
2	2
3	3
4	2
5	5
6	2
7	3
8	11
9	3
10	2
11	5
12	2
13	3
14	2
15	3
16	5
17	5
18	3
19	11
20	2
21	5
22	2
23	5
24	2
25	3
26	2
27	3
28	3
29	7
30	5
31	11
32	2
33	5
34	2
35	5
36	2
37	3
38	5
39	3
40	5
41	17
42	2
43	3
44	7
45	3
46	2
47	5
48	3
49	3
50	2
51	5
52	2
53	13
54	2
55	5
56	5
57	3
58	3
59	11
60	2
61	5
62	5
63	5
64	2
65	7
66	2
67	3
68	5
69	3
70	2
71	7
72	5
73	3
74	2
75	7
76	2
77	5
78	3
79	3
80	2
81	5
82	113
83	5
84	3
85	11