A235917 - cp's OEIS frontend

A235917 a(n) = |{0 < k < n - 2: p = prime(k) + phi(n-k)/2, p^2 - 1 - prime(p) and (p^2 - 1)/2 - prime(p) are all prime}|, where phi(.) is Euler's totient function.

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

[0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 2, 2, 0, 3, 1, 4, 2, 4, 3, 1, 2, 2, 3, 3, 1, 2, 2, 1, 1, 2, 4, 1, 5, 2, 2, 3, 2, 6, 2, 1, 3, 3, 2, 4, 5, 4, 2, 5, 3, 4, 2, 3, 4, 4, 3, 3, 2, 1, 4, 3, 2, 3, 4, 5, 7, 3, 5, 1, 6, 1, 7, 3, 6, 5, 3, 5, 2, 3, 4, 5, 3, 8, 6, 4, 2, 6, 4, 8, 3, 7, 5, 6, 6, 4, 3, 5, 6, 4, 3]

cp's OEIS Frontend

A235917 a(n) = |{0 < k < n - 2: p = prime(k) + phi(n-k)/2, p^2 - 1 - prime(p) and (p^2 - 1)/2 - prime(p) are all 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	0
7	0
8	1
9	0
10	1
11	1
12	2
13	2
14	0
15	3
16	1
17	4
18	2
19	4
20	3
21	1
22	2
23	2
24	3
25	3
26	1
27	2
28	2
29	1
30	1
31	2
32	4
33	1
34	5
35	2
36	2
37	3
38	2
39	6
40	2
41	1
42	3
43	3
44	2
45	4
46	5
47	4
48	2
49	5
50	3
51	4
52	2
53	3
54	4
55	4
56	3
57	3
58	2
59	1
60	4
61	3
62	2
63	3
64	4
65	5
66	7
67	3
68	5
69	1
70	6
71	1
72	7
73	3
74	6
75	5
76	3
77	5
78	2
79	3
80	4
81	5
82	3
83	8
84	6
85	4
86	2
87	6
88	4
89	8
90	3
91	7
92	5
93	6
94	6
95	4
96	3
97	5
98	6
99	4
100	3

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

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