A357481 - cp's OEIS frontend

A357481 a(n) is the least integer b such that the digit representation of n in base b is equal to the digit representation in base b of the initial terms of the sets of divisors of n in increasing order, or -1 if no such b exists.

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

[2, -1, -1, -1, -1, 2, -1, 6, 6, 8, -1, 10, -1, 12, 12, 14, -1, 16, -1, 18, 18, 20, -1, 22, 20, 24, 24, 26, -1, 28, -1, 30, 30, 32, 30, 34, -1, 36, 36, 38, -1, 40, -1, 42, 42, 44, -1, 3, 42, 3, 48, 2, -1, 52, 50, 54, 54, 56, -1, 58, -1, 60, 2, 62, 60, 7, -1, 66, 66, 68, -1, 70, -1, 72, 7]

cp's OEIS Frontend

A357481 a(n) is the least integer b such that the digit representation of n in base b is equal to the digit representation in base b of the initial terms of the sets of divisors of n in increasing order, or -1 if no such b exists.

Table of values

List of values

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

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

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