A234337 - cp's OEIS frontend

A234337 a(n) = |{0 < k < n - 2: 4^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	1
5	2
6	3
7	3
8	3
9	5
10	5
11	5
12	7
13	7
14	8
15	8
16	7
17	6
18	8
19	6
20	10
21	8
22	5
23	6
24	7
25	10
26	7
27	6
28	10
29	9
30	6
31	7
32	8
33	12
34	5
35	9
36	4
37	9
38	4
39	6
40	3
41	8
42	8
43	11
44	10
45	9
46	7
47	7
48	13
49	12
50	6
51	7
52	8
53	6
54	6
55	13
56	10
57	8
58	9
59	9
60	12
61	6
62	11
63	14
64	9
65	5
66	11
67	7
68	7
69	10
70	11
71	7
72	9
73	10
74	5
75	9
76	8
77	8
78	13
79	7
80	13

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

cp's OEIS Frontend

A234337 a(n) = |{0 < k < n - 2: 4^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	1
5	2
6	3
7	3
8	3
9	5
10	5
11	5
12	7
13	7
14	8
15	8
16	7
17	6
18	8
19	6
20	10
21	8
22	5
23	6
24	7
25	10
26	7
27	6
28	10
29	9
30	6
31	7
32	8
33	12
34	5
35	9
36	4
37	9
38	4
39	6
40	3
41	8
42	8
43	11
44	10
45	9
46	7
47	7
48	13
49	12
50	6
51	7
52	8
53	6
54	6
55	13
56	10
57	8
58	9
59	9
60	12
61	6
62	11
63	14
64	9
65	5
66	11
67	7
68	7
69	10
70	11
71	7
72	9
73	10
74	5
75	9
76	8
77	8
78	13
79	7
80	13

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

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