A238568 - cp's OEIS frontend

A238568 a(n) = |{0 < k < n: n^2 - pi(k*n) is prime}|, where pi(x) denotes the number of primes not exceeding x.

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

[0, 1, 1, 1, 2, 2, 2, 1, 2, 1, 3, 2, 4, 3, 4, 2, 2, 5, 5, 3, 4, 4, 8, 1, 3, 3, 4, 3, 4, 3, 6, 3, 4, 4, 3, 4, 6, 3, 5, 2, 1, 8, 3, 10, 6, 5, 5, 9, 7, 6, 3, 8, 7, 9, 2, 5, 5, 2, 2, 9, 7, 3, 5, 8, 7, 6, 8, 7, 9, 9, 6, 3, 7, 8, 14, 5, 9, 10, 8, 11]

cp's OEIS Frontend

A238568 a(n) = |{0 < k < n: n^2 - pi(k*n) is prime}|, where pi(x) denotes the number of primes not exceeding x.

Table of values

List of values

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

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

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