A237531 - cp's OEIS frontend

A237531 a(n) = |{0 < k < n/2: phi(k(n-k)) - 1 and phi(k(n-k)) + 1 are both prime}|, where phi(.) is Euler's totient function.

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

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

cp's OEIS Frontend

A237531 a(n) = |{0 < k < n/2: phi(k(n-k)) - 1 and phi(k(n-k)) + 1 are both 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	2
7	2
8	2
9	3
10	2
11	3
12	1
13	3
14	1
15	4
16	1
17	1
18	1
19	1
20	4
21	3
22	2
23	1
24	2
25	1
26	1
27	3
28	2
29	5
30	4
31	3
32	3
33	6
34	2
35	3
36	1
37	5
38	4
39	5
40	2
41	3
42	5
43	5
44	3
45	7
46	6
47	3
48	7
49	3
50	8
51	7
52	4
53	4
54	5
55	6
56	4
57	3
58	9
59	6
60	8
61	9
62	8
63	9
64	9
65	10
66	7
67	6
68	3
69	5
70	4
71	8
72	4
73	8
74	5
75	10
76	2
77	7
78	9
79	5
80	7

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

cp's OEIS Frontend

A237531 a(n) = |{0 < k < n/2: phi(k*(n-k)) - 1 and phi(k*(n-k)) + 1 are both prime}|, where phi(.) is Euler's totient function.

Table of values

List of values

A237531 a(n) = |{0 < k < n/2: phi(k(n-k)) - 1 and phi(k(n-k)) + 1 are both prime}|, where phi(.) is Euler's totient function.

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