A232270 - cp's OEIS frontend

A232270 Number of ways to write n = x + y (0 < x <= y) with sigma(x) + phi(y) prime, where sigma(x) is the sum of all (positive) divisors of x and phi is Euler's totient function.

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

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

cp's OEIS Frontend

A232270 Number of ways to write n = x + y (0 < x <= y) with sigma(x) + phi(y) prime, where sigma(x) is the sum of all (positive) divisors of x and phi is Euler's totient function.

Table of values

List of values

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

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

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