A376212 - cp's OEIS frontend

A376212 a(n) is the least k such that A001615(k) = 2*n, or -1 if there is no such k, where A001615 is the Dedekind psi function.

n	a(n)
1	-1
2	3
3	4
4	7
5	-1
6	6
7	13
8	-1
9	10
10	19
11	-1
12	12
13	-1
14	-1
15	25
16	21
17	-1
18	18
19	37
20	-1
21	26
22	43
23	-1
24	24
25	-1
26	-1
27	34
28	39
29	-1
30	38
31	61
32	-1
33	-1
34	67
35	-1
36	30
37	73
38	-1
39	-1
40	57
41	-1
42	52
43	-1
44	-1
45	50
46	-1
47	-1
48	42
49	97
50	-1
51	101
52	103
53	-1
54	54
55	109
56	91
57	74
58	-1
59	-1
60	75
61	-1
62	-1
63	82
64	93
65	-1
66	86
67	-1
68	-1
69	137
70	139
71	-1
72	60
73	-1
74	-1

[-1, 3, 4, 7, -1, 6, 13, -1, 10, 19, -1, 12, -1, -1, 25, 21, -1, 18, 37, -1, 26, 43, -1, 24, -1, -1, 34, 39, -1, 38, 61, -1, -1, 67, -1, 30, 73, -1, -1, 57, -1, 52, -1, -1, 50, -1, -1, 42, 97, -1, 101, 103, -1, 54, 109, 91, 74, -1, -1, 75, -1, -1, 82, 93, -1, 86, -1, -1, 137, 139, -1, 60, -1, -1]

cp's OEIS Frontend

A376212 a(n) is the least k such that A001615(k) = 2*n, or -1 if there is no such k, where A001615 is the Dedekind psi function.

Table of values

List of values

n	a(n)
1	-1
2	3
3	4
4	7
5	-1
6	6
7	13
8	-1
9	10
10	19
11	-1
12	12
13	-1
14	-1
15	25
16	21
17	-1
18	18
19	37
20	-1
21	26
22	43
23	-1
24	24
25	-1
26	-1
27	34
28	39
29	-1
30	38
31	61
32	-1
33	-1
34	67
35	-1
36	30
37	73
38	-1
39	-1
40	57
41	-1
42	52
43	-1
44	-1
45	50
46	-1
47	-1
48	42
49	97
50	-1
51	101
52	103
53	-1
54	54
55	109
56	91
57	74
58	-1
59	-1
60	75
61	-1
62	-1
63	82
64	93
65	-1
66	86
67	-1
68	-1
69	137
70	139
71	-1
72	60
73	-1
74	-1

n	a(n)
1	-1
2	3
3	4
4	7
5	-1
6	6
7	13
8	-1
9	10
10	19
11	-1
12	12
13	-1
14	-1
15	25
16	21
17	-1
18	18
19	37
20	-1
21	26
22	43
23	-1
24	24
25	-1
26	-1
27	34
28	39
29	-1
30	38
31	61
32	-1
33	-1
34	67
35	-1
36	30
37	73
38	-1
39	-1
40	57
41	-1
42	52
43	-1
44	-1
45	50
46	-1
47	-1
48	42
49	97
50	-1
51	101
52	103
53	-1
54	54
55	109
56	91
57	74
58	-1
59	-1
60	75
61	-1
62	-1
63	82
64	93
65	-1
66	86
67	-1
68	-1
69	137
70	139
71	-1
72	60
73	-1
74	-1

n	a(n)
1	-1
2	3
3	4
4	7
5	-1
6	6
7	13
8	-1
9	10
10	19
11	-1
12	12
13	-1
14	-1
15	25
16	21
17	-1
18	18
19	37
20	-1
21	26
22	43
23	-1
24	24
25	-1
26	-1
27	34
28	39
29	-1
30	38
31	61
32	-1
33	-1
34	67
35	-1
36	30
37	73
38	-1
39	-1
40	57
41	-1
42	52
43	-1
44	-1
45	50
46	-1
47	-1
48	42
49	97
50	-1
51	101
52	103
53	-1
54	54
55	109
56	91
57	74
58	-1
59	-1
60	75
61	-1
62	-1
63	82
64	93
65	-1
66	86
67	-1
68	-1
69	137
70	139
71	-1
72	60
73	-1
74	-1