A234359 - cp's OEIS frontend

A234359 a(n) = |{2 < k < n-2: 5^{phi(k)} + 5^{phi(n-k)/2} - 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	2
8	1
9	2
10	4
11	2
12	4
13	4
14	3
15	4
16	3
17	6
18	5
19	4
20	6
21	7
22	8
23	6
24	7
25	11
26	7
27	10
28	9
29	9
30	7
31	10
32	11
33	8
34	7
35	11
36	10
37	9
38	6
39	11
40	15
41	4
42	14
43	5
44	14
45	11
46	13
47	9
48	13
49	6
50	12
51	10
52	12
53	11
54	10
55	10
56	13
57	9
58	7
59	11
60	7
61	11
62	4
63	11
64	9
65	10
66	6
67	11
68	8
69	4
70	10
71	12
72	13
73	9
74	7
75	9
76	6
77	12
78	10

[0, 0, 0, 0, 0, 1, 2, 1, 2, 4, 2, 4, 4, 3, 4, 3, 6, 5, 4, 6, 7, 8, 6, 7, 11, 7, 10, 9, 9, 7, 10, 11, 8, 7, 11, 10, 9, 6, 11, 15, 4, 14, 5, 14, 11, 13, 9, 13, 6, 12, 10, 12, 11, 10, 10, 13, 9, 7, 11, 7, 11, 4, 11, 9, 10, 6, 11, 8, 4, 10, 12, 13, 9, 7, 9, 6, 12, 10]

cp's OEIS Frontend

A234359 a(n) = |{2 < k < n-2: 5^{phi(k)} + 5^{phi(n-k)/2} - 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	2
8	1
9	2
10	4
11	2
12	4
13	4
14	3
15	4
16	3
17	6
18	5
19	4
20	6
21	7
22	8
23	6
24	7
25	11
26	7
27	10
28	9
29	9
30	7
31	10
32	11
33	8
34	7
35	11
36	10
37	9
38	6
39	11
40	15
41	4
42	14
43	5
44	14
45	11
46	13
47	9
48	13
49	6
50	12
51	10
52	12
53	11
54	10
55	10
56	13
57	9
58	7
59	11
60	7
61	11
62	4
63	11
64	9
65	10
66	6
67	11
68	8
69	4
70	10
71	12
72	13
73	9
74	7
75	9
76	6
77	12
78	10

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

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