A261625 - cp's OEIS frontend

A261625 Number of primes p <= n such that (p-1)*n+1 is prime.

n	a(n)
1	0
2	1
3	1
4	1
5	1
6	2
7	2
8	1
9	2
10	3
11	2
12	2
13	4
14	1
15	4
16	3
17	1
18	5
19	2
20	2
21	5
22	4
23	3
24	3
25	4
26	3
27	5
28	6
29	3
30	5
31	3
32	2
33	6
34	5
35	5
36	5
37	3
38	2
39	5
40	6
41	3
42	4
43	6
44	2
45	7
46	9
47	2
48	5
49	5
50	3
51	9
52	7
53	1
54	5
55	7
56	5
57	5
58	8
59	2
60	8
61	7
62	3
63	8
64	7
65	5
66	7
67	6
68	3
69	6
70	9
71	5
72	9
73	7
74	4
75	6
76	8
77	3
78	8
79	9
80	3

[0, 1, 1, 1, 1, 2, 2, 1, 2, 3, 2, 2, 4, 1, 4, 3, 1, 5, 2, 2, 5, 4, 3, 3, 4, 3, 5, 6, 3, 5, 3, 2, 6, 5, 5, 5, 3, 2, 5, 6, 3, 4, 6, 2, 7, 9, 2, 5, 5, 3, 9, 7, 1, 5, 7, 5, 5, 8, 2, 8, 7, 3, 8, 7, 5, 7, 6, 3, 6, 9, 5, 9, 7, 4, 6, 8, 3, 8, 9, 3]

cp's OEIS Frontend

A261625 Number of primes p <= n such that (p-1)*n+1 is prime.

Table of values

List of values

n	a(n)
1	0
2	1
3	1
4	1
5	1
6	2
7	2
8	1
9	2
10	3
11	2
12	2
13	4
14	1
15	4
16	3
17	1
18	5
19	2
20	2
21	5
22	4
23	3
24	3
25	4
26	3
27	5
28	6
29	3
30	5
31	3
32	2
33	6
34	5
35	5
36	5
37	3
38	2
39	5
40	6
41	3
42	4
43	6
44	2
45	7
46	9
47	2
48	5
49	5
50	3
51	9
52	7
53	1
54	5
55	7
56	5
57	5
58	8
59	2
60	8
61	7
62	3
63	8
64	7
65	5
66	7
67	6
68	3
69	6
70	9
71	5
72	9
73	7
74	4
75	6
76	8
77	3
78	8
79	9
80	3

n	a(n)
1	0
2	1
3	1
4	1
5	1
6	2
7	2
8	1
9	2
10	3
11	2
12	2
13	4
14	1
15	4
16	3
17	1
18	5
19	2
20	2
21	5
22	4
23	3
24	3
25	4
26	3
27	5
28	6
29	3
30	5
31	3
32	2
33	6
34	5
35	5
36	5
37	3
38	2
39	5
40	6
41	3
42	4
43	6
44	2
45	7
46	9
47	2
48	5
49	5
50	3
51	9
52	7
53	1
54	5
55	7
56	5
57	5
58	8
59	2
60	8
61	7
62	3
63	8
64	7
65	5
66	7
67	6
68	3
69	6
70	9
71	5
72	9
73	7
74	4
75	6
76	8
77	3
78	8
79	9
80	3

n	a(n)
1	0
2	1
3	1
4	1
5	1
6	2
7	2
8	1
9	2
10	3
11	2
12	2
13	4
14	1
15	4
16	3
17	1
18	5
19	2
20	2
21	5
22	4
23	3
24	3
25	4
26	3
27	5
28	6
29	3
30	5
31	3
32	2
33	6
34	5
35	5
36	5
37	3
38	2
39	5
40	6
41	3
42	4
43	6
44	2
45	7
46	9
47	2
48	5
49	5
50	3
51	9
52	7
53	1
54	5
55	7
56	5
57	5
58	8
59	2
60	8
61	7
62	3
63	8
64	7
65	5
66	7
67	6
68	3
69	6
70	9
71	5
72	9
73	7
74	4
75	6
76	8
77	3
78	8
79	9
80	3