A347982 - cp's OEIS frontend

A347982 a(n) is the greatest k, 0 < k < n, such that tau(k) = tau(n), or -1 if no such k exists, where tau is A000005.

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

[-1, -1, 2, -1, 3, -1, 5, 6, 4, 8, 7, -1, 11, 10, 14, -1, 13, 12, 17, 18, 15, 21, 19, -1, 9, 22, 26, 20, 23, 24, 29, 28, 27, 33, 34, -1, 31, 35, 38, 30, 37, 40, 41, 32, 44, 39, 43, -1, 25, 45, 46, 50, 47, 42, 51, 54, 55, 57, 53, -1, 59, 58, 52, -1, 62, 56, 61, 63, 65, 66, 67]

cp's OEIS Frontend

A347982 a(n) is the greatest k, 0 < k < n, such that tau(k) = tau(n), or -1 if no such k exists, where tau is A000005.

Table of values

List of values

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

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

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