A109909 - cp's OEIS frontend

A109909 a(n) = number of primes of the form k*(n-k)-1.

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

[0, 0, 0, 2, 2, 1, 2, 1, 4, 1, 3, 2, 3, 2, 3, 2, 4, 3, 5, 1, 10, 1, 5, 5, 4, 2, 6, 3, 5, 3, 9, 4, 11, 3, 5, 5, 5, 5, 14, 1, 6, 6, 7, 6, 11, 5, 8, 4, 15, 3, 13, 4, 10, 9, 6, 5, 11, 4, 12, 5, 13, 4, 12, 4, 6, 11, 13, 4, 12, 6, 15, 12, 9, 4, 9, 5, 10, 8, 10, 3, 28, 7, 11, 15, 6, 9, 20, 7, 20, 6, 17, 5, 23]

cp's OEIS Frontend

A109909 a(n) = number of primes of the form k*(n-k)-1.

Table of values

List of values

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

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

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