A233566 - cp's OEIS frontend

A233566 a(n) = |{0 < p < n: p and p*phi(n-p) - 1 are both prime}|, where phi(.) is Euler's totient function (A000010).

n	a(n)
1	0
2	0
3	0
4	1
5	2
6	2
7	2
8	2
9	2
10	4
11	3
12	3
13	4
14	4
15	3
16	3
17	2
18	2
19	4
20	3
21	3
22	5
23	5
24	4
25	5
26	3
27	2
28	6
29	2
30	4
31	2
32	7
33	7
34	8
35	5
36	4
37	8
38	4
39	4
40	8
41	5
42	5
43	8
44	4
45	4
46	5
47	6
48	5
49	5
50	10
51	7
52	8
53	4
54	4
55	5
56	6
57	8
58	7
59	4
60	6
61	6
62	9
63	11
64	7
65	10
66	4
67	6
68	7
69	8
70	10
71	4
72	7
73	6
74	5
75	5
76	12
77	8
78	8
79	7
80	11
81	13
82	11
83	12
84	5
85	8
86	7
87	11
88	9
89	5
90	8
91	5
92	6
93	12
94	8
95	8
96	5
97	9
98	5
99	11
100	12

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

cp's OEIS Frontend

A233566 a(n) = |{0 < p < n: p and p*phi(n-p) - 1 are both prime}|, where phi(.) is Euler's totient function (A000010).

Table of values

List of values

n	a(n)
1	0
2	0
3	0
4	1
5	2
6	2
7	2
8	2
9	2
10	4
11	3
12	3
13	4
14	4
15	3
16	3
17	2
18	2
19	4
20	3
21	3
22	5
23	5
24	4
25	5
26	3
27	2
28	6
29	2
30	4
31	2
32	7
33	7
34	8
35	5
36	4
37	8
38	4
39	4
40	8
41	5
42	5
43	8
44	4
45	4
46	5
47	6
48	5
49	5
50	10
51	7
52	8
53	4
54	4
55	5
56	6
57	8
58	7
59	4
60	6
61	6
62	9
63	11
64	7
65	10
66	4
67	6
68	7
69	8
70	10
71	4
72	7
73	6
74	5
75	5
76	12
77	8
78	8
79	7
80	11
81	13
82	11
83	12
84	5
85	8
86	7
87	11
88	9
89	5
90	8
91	5
92	6
93	12
94	8
95	8
96	5
97	9
98	5
99	11
100	12

n	a(n)
1	0
2	0
3	0
4	1
5	2
6	2
7	2
8	2
9	2
10	4
11	3
12	3
13	4
14	4
15	3
16	3
17	2
18	2
19	4
20	3
21	3
22	5
23	5
24	4
25	5
26	3
27	2
28	6
29	2
30	4
31	2
32	7
33	7
34	8
35	5
36	4
37	8
38	4
39	4
40	8
41	5
42	5
43	8
44	4
45	4
46	5
47	6
48	5
49	5
50	10
51	7
52	8
53	4
54	4
55	5
56	6
57	8
58	7
59	4
60	6
61	6
62	9
63	11
64	7
65	10
66	4
67	6
68	7
69	8
70	10
71	4
72	7
73	6
74	5
75	5
76	12
77	8
78	8
79	7
80	11
81	13
82	11
83	12
84	5
85	8
86	7
87	11
88	9
89	5
90	8
91	5
92	6
93	12
94	8
95	8
96	5
97	9
98	5
99	11
100	12

n	a(n)
1	0
2	0
3	0
4	1
5	2
6	2
7	2
8	2
9	2
10	4
11	3
12	3
13	4
14	4
15	3
16	3
17	2
18	2
19	4
20	3
21	3
22	5
23	5
24	4
25	5
26	3
27	2
28	6
29	2
30	4
31	2
32	7
33	7
34	8
35	5
36	4
37	8
38	4
39	4
40	8
41	5
42	5
43	8
44	4
45	4
46	5
47	6
48	5
49	5
50	10
51	7
52	8
53	4
54	4
55	5
56	6
57	8
58	7
59	4
60	6
61	6
62	9
63	11
64	7
65	10
66	4
67	6
68	7
69	8
70	10
71	4
72	7
73	6
74	5
75	5
76	12
77	8
78	8
79	7
80	11
81	13
82	11
83	12
84	5
85	8
86	7
87	11
88	9
89	5
90	8
91	5
92	6
93	12
94	8
95	8
96	5
97	9
98	5
99	11
100	12