A237615 - cp's OEIS frontend

A237615 a(n) = |{0 < k < n: k^2 + k - 1 and pi(k*n) are both prime}|, where pi(.) is given by A000720.

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

[0, 0, 1, 1, 0, 2, 2, 1, 2, 1, 3, 2, 1, 4, 1, 3, 4, 4, 2, 4, 3, 6, 2, 2, 2, 3, 7, 4, 3, 4, 5, 6, 1, 3, 2, 3, 9, 3, 3, 4, 7, 5, 8, 5, 2, 2, 5, 5, 4, 5, 6, 4, 5, 6, 10, 6, 6, 10, 9, 9, 10, 12, 2, 8, 7, 3, 6, 6, 4, 6]

cp's OEIS Frontend

A237615 a(n) = |{0 < k < n: k^2 + k - 1 and pi(k*n) are both prime}|, where pi(.) is given by A000720.

Table of values

List of values

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

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

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