A234809 - cp's OEIS frontend

A234809 a(n) = |{0 < k < n: p = k + phi(n-k) and 2*(n-p) + 1 are both prime}|, where phi(.) is Euler's totient function.

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

[0, 0, 1, 2, 1, 3, 1, 4, 1, 1, 1, 5, 3, 7, 3, 1, 1, 7, 5, 9, 4, 2, 1, 9, 5, 2, 4, 3, 1, 10, 5, 14, 2, 2, 2, 1, 6, 14, 5, 4, 1, 15, 5, 16, 5, 5, 3, 17, 8, 4, 5, 6, 3, 17, 7, 5, 2, 6, 6, 17, 11, 25, 3, 5, 3, 1, 11, 25, 4, 4, 4, 22, 10, 26, 6, 7, 8, 3, 9, 26, 7, 9, 6, 25, 8, 3, 7, 9, 10, 25, 15, 6, 2, 9, 9, 2, 13, 29, 3, 7]

cp's OEIS Frontend

A234809 a(n) = |{0 < k < n: p = k + phi(n-k) and 2*(n-p) + 1 are both prime}|, where phi(.) is Euler's totient function.

Table of values

List of values

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

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

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