A261653 - cp's OEIS frontend

A261653 Number of primes p < n such that n-p-1 and n+p+1 are both prime or both practical.

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

[0, 0, 0, 0, 1, 0, 1, 2, 2, 3, 2, 3, 1, 2, 3, 5, 3, 3, 1, 4, 2, 4, 3, 5, 3, 3, 4, 4, 3, 4, 1, 3, 4, 5, 5, 7, 3, 1, 4, 6, 4, 7, 2, 4, 4, 5, 3, 8, 3, 4, 5, 6, 3, 6, 5, 6, 4, 4, 5, 9, 3, 2, 4, 7, 6, 10, 3, 6, 4, 6, 6, 10, 3, 3, 7, 7, 7, 9, 4, 6]

cp's OEIS Frontend

A261653 Number of primes p < n such that n-p-1 and n+p+1 are both prime or both practical.

Table of values

List of values

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

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

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