A305818 - cp's OEIS frontend

A305818 Number of proper divisors d of n such that 2d+1 is a prime.

n	a(n)
1	0
2	1
3	1
4	2
5	1
6	3
7	1
8	2
9	2
10	3
11	1
12	4
13	1
14	2
15	3
16	3
17	1
18	5
19	1
20	3
21	2
22	3
23	1
24	5
25	2
26	2
27	3
28	3
29	1
30	6
31	1
32	3
33	3
34	2
35	2
36	6
37	1
38	2
39	2
40	5
41	1
42	6
43	1
44	3
45	5
46	3
47	1
48	5
49	1
50	3
51	2
52	3
53	1
54	6
55	3
56	4
57	2
58	3
59	1
60	8
61	1
62	2
63	4
64	3
65	2
66	6
67	1
68	2
69	3
70	5
71	1
72	8
73	1
74	2
75	4
76	2
77	2
78	6
79	1
80	5
81	3
82	3
83	1
84	6
85	2
86	2
87	3
88	5
89	1
90	9
91	1
92	3
93	2
94	2
95	2
96	6
97	1
98	3
99	5
100	5
101	1
102	5
103	1
104	4
105	6

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

cp's OEIS Frontend

A305818 Number of proper divisors d of n such that 2d+1 is a prime.

Table of values

List of values

n	a(n)
1	0
2	1
3	1
4	2
5	1
6	3
7	1
8	2
9	2
10	3
11	1
12	4
13	1
14	2
15	3
16	3
17	1
18	5
19	1
20	3
21	2
22	3
23	1
24	5
25	2
26	2
27	3
28	3
29	1
30	6
31	1
32	3
33	3
34	2
35	2
36	6
37	1
38	2
39	2
40	5
41	1
42	6
43	1
44	3
45	5
46	3
47	1
48	5
49	1
50	3
51	2
52	3
53	1
54	6
55	3
56	4
57	2
58	3
59	1
60	8
61	1
62	2
63	4
64	3
65	2
66	6
67	1
68	2
69	3
70	5
71	1
72	8
73	1
74	2
75	4
76	2
77	2
78	6
79	1
80	5
81	3
82	3
83	1
84	6
85	2
86	2
87	3
88	5
89	1
90	9
91	1
92	3
93	2
94	2
95	2
96	6
97	1
98	3
99	5
100	5
101	1
102	5
103	1
104	4
105	6

n	a(n)
1	0
2	1
3	1
4	2
5	1
6	3
7	1
8	2
9	2
10	3
11	1
12	4
13	1
14	2
15	3
16	3
17	1
18	5
19	1
20	3
21	2
22	3
23	1
24	5
25	2
26	2
27	3
28	3
29	1
30	6
31	1
32	3
33	3
34	2
35	2
36	6
37	1
38	2
39	2
40	5
41	1
42	6
43	1
44	3
45	5
46	3
47	1
48	5
49	1
50	3
51	2
52	3
53	1
54	6
55	3
56	4
57	2
58	3
59	1
60	8
61	1
62	2
63	4
64	3
65	2
66	6
67	1
68	2
69	3
70	5
71	1
72	8
73	1
74	2
75	4
76	2
77	2
78	6
79	1
80	5
81	3
82	3
83	1
84	6
85	2
86	2
87	3
88	5
89	1
90	9
91	1
92	3
93	2
94	2
95	2
96	6
97	1
98	3
99	5
100	5
101	1
102	5
103	1
104	4
105	6

n	a(n)
1	0
2	1
3	1
4	2
5	1
6	3
7	1
8	2
9	2
10	3
11	1
12	4
13	1
14	2
15	3
16	3
17	1
18	5
19	1
20	3
21	2
22	3
23	1
24	5
25	2
26	2
27	3
28	3
29	1
30	6
31	1
32	3
33	3
34	2
35	2
36	6
37	1
38	2
39	2
40	5
41	1
42	6
43	1
44	3
45	5
46	3
47	1
48	5
49	1
50	3
51	2
52	3
53	1
54	6
55	3
56	4
57	2
58	3
59	1
60	8
61	1
62	2
63	4
64	3
65	2
66	6
67	1
68	2
69	3
70	5
71	1
72	8
73	1
74	2
75	4
76	2
77	2
78	6
79	1
80	5
81	3
82	3
83	1
84	6
85	2
86	2
87	3
88	5
89	1
90	9
91	1
92	3
93	2
94	2
95	2
96	6
97	1
98	3
99	5
100	5
101	1
102	5
103	1
104	4
105	6