A238580 - cp's OEIS frontend

A238580 a(n) = |{0 < k <= n: 2k + 1 and prime(k)prime(n) - 2 are both prime}|.

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

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

cp's OEIS Frontend

A238580 a(n) = |{0 < k <= n: 2k + 1 and prime(k)prime(n) - 2 are both prime}|.

Table of values

List of values

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

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

cp's OEIS Frontend

A238580 a(n) = |{0 < k <= n: 2*k + 1 and prime(k)*prime(n) - 2 are both prime}|.

Table of values

List of values

A238580 a(n) = |{0 < k <= n: 2k + 1 and prime(k)prime(n) - 2 are both prime}|.

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