A238504 - cp's OEIS frontend

A238504 Number of primes p <= n with pi(pi((p-1)*n)) prime, where pi(x) denotes the number of primes not exceeding x.

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

[0, 0, 1, 1, 2, 2, 2, 3, 2, 3, 2, 1, 3, 2, 4, 3, 1, 2, 3, 1, 1, 2, 1, 2, 2, 1, 1, 4, 1, 2, 4, 4, 5, 5, 3, 4, 4, 6, 4, 2, 1, 1, 3, 4, 6, 4, 4, 1, 3, 3, 2, 4, 6, 2, 2, 3, 3, 3, 4, 10, 5, 6, 7, 5, 4, 5, 5, 3, 5, 6, 6, 5, 5, 4, 5, 6, 6, 4, 3, 4]

cp's OEIS Frontend

A238504 Number of primes p <= n with pi(pi((p-1)*n)) prime, where pi(x) denotes the number of primes not exceeding x.

Table of values

List of values

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

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

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