A235919 - cp's OEIS frontend

A235919 a(n) = |{0 < k < n - 2: p = prime(k) + phi(n-k)/2, prime(p) - p + 1 and (p^2 - 1)/4 - 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	0
9	0
10	0
11	0
12	0
13	0
14	0
15	1
16	0
17	0
18	3
19	0
20	1
21	2
22	3
23	1
24	0
25	3
26	3
27	2
28	1
29	2
30	1
31	3
32	2
33	4
34	2
35	1
36	6
37	2
38	6
39	2
40	3
41	2
42	3
43	6
44	2
45	1
46	7
47	2
48	5
49	4
50	3
51	4
52	3
53	6
54	4
55	5
56	4
57	2
58	1
59	2
60	8
61	2
62	4
63	5
64	5
65	6
66	4
67	5
68	4
69	6
70	3
71	3
72	5
73	6
74	5
75	3
76	4
77	8
78	2
79	3
80	7
81	7
82	8
83	5
84	5
85	3
86	3
87	7
88	9
89	3
90	8
91	2
92	4
93	4
94	4
95	9
96	2
97	5
98	8
99	5
100	5

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 3, 0, 1, 2, 3, 1, 0, 3, 3, 2, 1, 2, 1, 3, 2, 4, 2, 1, 6, 2, 6, 2, 3, 2, 3, 6, 2, 1, 7, 2, 5, 4, 3, 4, 3, 6, 4, 5, 4, 2, 1, 2, 8, 2, 4, 5, 5, 6, 4, 5, 4, 6, 3, 3, 5, 6, 5, 3, 4, 8, 2, 3, 7, 7, 8, 5, 5, 3, 3, 7, 9, 3, 8, 2, 4, 4, 4, 9, 2, 5, 8, 5, 5]

cp's OEIS Frontend

A235919 a(n) = |{0 < k < n - 2: p = prime(k) + phi(n-k)/2, prime(p) - p + 1 and (p^2 - 1)/4 - 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	0
9	0
10	0
11	0
12	0
13	0
14	0
15	1
16	0
17	0
18	3
19	0
20	1
21	2
22	3
23	1
24	0
25	3
26	3
27	2
28	1
29	2
30	1
31	3
32	2
33	4
34	2
35	1
36	6
37	2
38	6
39	2
40	3
41	2
42	3
43	6
44	2
45	1
46	7
47	2
48	5
49	4
50	3
51	4
52	3
53	6
54	4
55	5
56	4
57	2
58	1
59	2
60	8
61	2
62	4
63	5
64	5
65	6
66	4
67	5
68	4
69	6
70	3
71	3
72	5
73	6
74	5
75	3
76	4
77	8
78	2
79	3
80	7
81	7
82	8
83	5
84	5
85	3
86	3
87	7
88	9
89	3
90	8
91	2
92	4
93	4
94	4
95	9
96	2
97	5
98	8
99	5
100	5

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

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