A233864 - cp's OEIS frontend

A233864 a(n) = |{0 < m < 2n: m = sigma(k) for some k > 0, and 2n - 1 - m and 2*n - 1 + m are both prime}|, where sigma(k) is the sum of all (positive) divisors of k.

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

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

cp's OEIS Frontend

A233864 a(n) = |{0 < m < 2n: m = sigma(k) for some k > 0, and 2n - 1 - m and 2*n - 1 + m are both prime}|, where sigma(k) is the sum of all (positive) divisors of k.

Table of values

List of values

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

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

cp's OEIS Frontend

A233864 a(n) = |{0 < m < 2*n: m = sigma(k) for some k > 0, and 2*n - 1 - m and 2*n - 1 + m are both prime}|, where sigma(k) is the sum of all (positive) divisors of k.

Table of values

List of values

A233864 a(n) = |{0 < m < 2n: m = sigma(k) for some k > 0, and 2n - 1 - m and 2*n - 1 + m are both prime}|, where sigma(k) is the sum of all (positive) divisors of k.

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