A234309 - cp's OEIS frontend

A234309 a(n) = |{2 < k <= n/2: 2^{phi(k)} + 2^{phi(n-k)} - 1 is prime}|, where phi(.) is Euler's totient function.

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	1
7	1
8	2
9	2
10	3
11	3
12	4
13	4
14	4
15	4
16	6
17	5
18	6
19	5
20	7
21	7
22	6
23	7
24	7
25	8
26	7
27	7
28	6
29	6
30	7
31	9
32	9
33	6
34	9
35	12
36	8
37	6
38	9
39	9
40	9
41	8
42	10
43	8
44	9
45	6
46	9
47	8
48	8
49	10
50	6
51	8
52	11
53	8
54	11
55	8
56	7
57	10
58	8
59	7
60	8
61	7
62	9
63	9
64	11
65	11
66	8
67	8
68	9
69	10
70	12
71	7
72	12
73	10
74	8
75	5
76	7
77	9
78	14
79	9
80	9
81	9
82	8
83	7

[0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 4, 4, 6, 5, 6, 5, 7, 7, 6, 7, 7, 8, 7, 7, 6, 6, 7, 9, 9, 6, 9, 12, 8, 6, 9, 9, 9, 8, 10, 8, 9, 6, 9, 8, 8, 10, 6, 8, 11, 8, 11, 8, 7, 10, 8, 7, 8, 7, 9, 9, 11, 11, 8, 8, 9, 10, 12, 7, 12, 10, 8, 5, 7, 9, 14, 9, 9, 9, 8, 7]

cp's OEIS Frontend

A234309 a(n) = |{2 < k <= n/2: 2^{phi(k)} + 2^{phi(n-k)} - 1 is prime}|, where phi(.) is Euler's totient function.

Table of values

List of values

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	1
7	1
8	2
9	2
10	3
11	3
12	4
13	4
14	4
15	4
16	6
17	5
18	6
19	5
20	7
21	7
22	6
23	7
24	7
25	8
26	7
27	7
28	6
29	6
30	7
31	9
32	9
33	6
34	9
35	12
36	8
37	6
38	9
39	9
40	9
41	8
42	10
43	8
44	9
45	6
46	9
47	8
48	8
49	10
50	6
51	8
52	11
53	8
54	11
55	8
56	7
57	10
58	8
59	7
60	8
61	7
62	9
63	9
64	11
65	11
66	8
67	8
68	9
69	10
70	12
71	7
72	12
73	10
74	8
75	5
76	7
77	9
78	14
79	9
80	9
81	9
82	8
83	7

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	1
7	1
8	2
9	2
10	3
11	3
12	4
13	4
14	4
15	4
16	6
17	5
18	6
19	5
20	7
21	7
22	6
23	7
24	7
25	8
26	7
27	7
28	6
29	6
30	7
31	9
32	9
33	6
34	9
35	12
36	8
37	6
38	9
39	9
40	9
41	8
42	10
43	8
44	9
45	6
46	9
47	8
48	8
49	10
50	6
51	8
52	11
53	8
54	11
55	8
56	7
57	10
58	8
59	7
60	8
61	7
62	9
63	9
64	11
65	11
66	8
67	8
68	9
69	10
70	12
71	7
72	12
73	10
74	8
75	5
76	7
77	9
78	14
79	9
80	9
81	9
82	8
83	7

n	a(n)
1	0
2	0
3	0
4	0
5	0
6	1
7	1
8	2
9	2
10	3
11	3
12	4
13	4
14	4
15	4
16	6
17	5
18	6
19	5
20	7
21	7
22	6
23	7
24	7
25	8
26	7
27	7
28	6
29	6
30	7
31	9
32	9
33	6
34	9
35	12
36	8
37	6
38	9
39	9
40	9
41	8
42	10
43	8
44	9
45	6
46	9
47	8
48	8
49	10
50	6
51	8
52	11
53	8
54	11
55	8
56	7
57	10
58	8
59	7
60	8
61	7
62	9
63	9
64	11
65	11
66	8
67	8
68	9
69	10
70	12
71	7
72	12
73	10
74	8
75	5
76	7
77	9
78	14
79	9
80	9
81	9
82	8
83	7