A015710 - cp's OEIS frontend

A015710 Least k >= 0 such that phi(n) * sigma(n) + k^2 is a perfect square, or -1 if impossible.

n	a(n)
1	0
2	1
3	1
4	-1
5	1
6	1
7	1
8	2
9	-1
10	3
11	1
12	3
13	1
14	0
15	2
16	29
17	1
18	-1
19	1
20	5
21	4
22	1
23	1
24	2
25	26
26	5
27	3
28	2
29	1
30	0
31	1
32	4
33	1
34	6
35	2
36	8
37	1
38	3
39	5
40	2
41	1
42	2
43	1
44	1
45	8
46	4
47	1
48	15
49	-1
50	16
51	0
52	7
53	1
54	7
55	6
56	6
57	6
58	9
59	1
60	4
61	1
62	6
63	10
64	119
65	8
66	6
67	1
68	8
69	1
70	5
71	1
72	9
73	1
74	11
75	9
76	1
77	4
78	8
79	1
80	17
81	-1
82	1

[0, 1, 1, -1, 1, 1, 1, 2, -1, 3, 1, 3, 1, 0, 2, 29, 1, -1, 1, 5, 4, 1, 1, 2, 26, 5, 3, 2, 1, 0, 1, 4, 1, 6, 2, 8, 1, 3, 5, 2, 1, 2, 1, 1, 8, 4, 1, 15, -1, 16, 0, 7, 1, 7, 6, 6, 6, 9, 1, 4, 1, 6, 10, 119, 8, 6, 1, 8, 1, 5, 1, 9, 1, 11, 9, 1, 4, 8, 1, 17, -1, 1]

cp's OEIS Frontend

A015710 Least k >= 0 such that phi(n) * sigma(n) + k^2 is a perfect square, or -1 if impossible.

Table of values

List of values

n	a(n)
1	0
2	1
3	1
4	-1
5	1
6	1
7	1
8	2
9	-1
10	3
11	1
12	3
13	1
14	0
15	2
16	29
17	1
18	-1
19	1
20	5
21	4
22	1
23	1
24	2
25	26
26	5
27	3
28	2
29	1
30	0
31	1
32	4
33	1
34	6
35	2
36	8
37	1
38	3
39	5
40	2
41	1
42	2
43	1
44	1
45	8
46	4
47	1
48	15
49	-1
50	16
51	0
52	7
53	1
54	7
55	6
56	6
57	6
58	9
59	1
60	4
61	1
62	6
63	10
64	119
65	8
66	6
67	1
68	8
69	1
70	5
71	1
72	9
73	1
74	11
75	9
76	1
77	4
78	8
79	1
80	17
81	-1
82	1

n	a(n)
1	0
2	1
3	1
4	-1
5	1
6	1
7	1
8	2
9	-1
10	3
11	1
12	3
13	1
14	0
15	2
16	29
17	1
18	-1
19	1
20	5
21	4
22	1
23	1
24	2
25	26
26	5
27	3
28	2
29	1
30	0
31	1
32	4
33	1
34	6
35	2
36	8
37	1
38	3
39	5
40	2
41	1
42	2
43	1
44	1
45	8
46	4
47	1
48	15
49	-1
50	16
51	0
52	7
53	1
54	7
55	6
56	6
57	6
58	9
59	1
60	4
61	1
62	6
63	10
64	119
65	8
66	6
67	1
68	8
69	1
70	5
71	1
72	9
73	1
74	11
75	9
76	1
77	4
78	8
79	1
80	17
81	-1
82	1

n	a(n)
1	0
2	1
3	1
4	-1
5	1
6	1
7	1
8	2
9	-1
10	3
11	1
12	3
13	1
14	0
15	2
16	29
17	1
18	-1
19	1
20	5
21	4
22	1
23	1
24	2
25	26
26	5
27	3
28	2
29	1
30	0
31	1
32	4
33	1
34	6
35	2
36	8
37	1
38	3
39	5
40	2
41	1
42	2
43	1
44	1
45	8
46	4
47	1
48	15
49	-1
50	16
51	0
52	7
53	1
54	7
55	6
56	6
57	6
58	9
59	1
60	4
61	1
62	6
63	10
64	119
65	8
66	6
67	1
68	8
69	1
70	5
71	1
72	9
73	1
74	11
75	9
76	1
77	4
78	8
79	1
80	17
81	-1
82	1