A237016 - cp's OEIS frontend

A237016 a(n) = |{0 < k < n: phi(k)*sigma(n-k) is a square}|, where phi(.) is Euler's totient function and sigma(j) is the sum of all positive divisors of j.

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

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

cp's OEIS Frontend

A237016 a(n) = |{0 < k < n: phi(k)*sigma(n-k) is a square}|, where phi(.) is Euler's totient function and sigma(j) is the sum of all positive divisors of j.

Table of values

List of values

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

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

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