A237497 - cp's OEIS frontend

A237497 a(n) = |{0 < k <= n/2: pi(k*(n-k)) is prime}|, where pi(.) is given by A000720.

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

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

cp's OEIS Frontend

A237497 a(n) = |{0 < k <= n/2: pi(k*(n-k)) is prime}|, where pi(.) is given by A000720.

Table of values

List of values

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

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

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