A347037 - cp's OEIS frontend

A347037 The length of the sequence before a repeated number appears, or -1 if a repeat never occurs, starting at k = n for the iterative cycle k -> sigma(k) - k if k is even, k -> sigma(k) if k is odd, where sigma(k) = sum of divisors of k.

n	a(n)
1	1
2	2
3	2
4	2
5	2
6	1
7	2
8	2
9	6
10	3
11	245
12	244
13	5
14	4
15	242
16	243
17	5
18	4
19	7
20	6
21	3
22	5
23	242
24	241
25	3
26	244
27	5
28	1
29	22
30	21
31	2
32	8
33	7
34	8
35	240
36	7
37	6
38	6
39	4
40	21
41	20
42	4
43	18
44	245
45	8
46	7
47	8
48	4
49	239
50	246
51	20
52	19
53	239
54	5
55	7
56	3
57	12
58	11
59	9
60	8
61	5
62	5
63	468
64	18
65	5
66	4
67	471
68	6
69	239
70	238
71	6
72	5
73	13
74	6
75	471
76	17
77	7
78	6
79	14
80	5
81	468

[1, 2, 2, 2, 2, 1, 2, 2, 6, 3, 245, 244, 5, 4, 242, 243, 5, 4, 7, 6, 3, 5, 242, 241, 3, 244, 5, 1, 22, 21, 2, 8, 7, 8, 240, 7, 6, 6, 4, 21, 20, 4, 18, 245, 8, 7, 8, 4, 239, 246, 20, 19, 239, 5, 7, 3, 12, 11, 9, 8, 5, 5, 468, 18, 5, 4, 471, 6, 239, 238, 6, 5, 13, 6, 471, 17, 7, 6, 14, 5, 468]

cp's OEIS Frontend

A347037 The length of the sequence before a repeated number appears, or -1 if a repeat never occurs, starting at k = n for the iterative cycle k -> sigma(k) - k if k is even, k -> sigma(k) if k is odd, where sigma(k) = sum of divisors of k.

Table of values

List of values

n	a(n)
1	1
2	2
3	2
4	2
5	2
6	1
7	2
8	2
9	6
10	3
11	245
12	244
13	5
14	4
15	242
16	243
17	5
18	4
19	7
20	6
21	3
22	5
23	242
24	241
25	3
26	244
27	5
28	1
29	22
30	21
31	2
32	8
33	7
34	8
35	240
36	7
37	6
38	6
39	4
40	21
41	20
42	4
43	18
44	245
45	8
46	7
47	8
48	4
49	239
50	246
51	20
52	19
53	239
54	5
55	7
56	3
57	12
58	11
59	9
60	8
61	5
62	5
63	468
64	18
65	5
66	4
67	471
68	6
69	239
70	238
71	6
72	5
73	13
74	6
75	471
76	17
77	7
78	6
79	14
80	5
81	468

n	a(n)
1	1
2	2
3	2
4	2
5	2
6	1
7	2
8	2
9	6
10	3
11	245
12	244
13	5
14	4
15	242
16	243
17	5
18	4
19	7
20	6
21	3
22	5
23	242
24	241
25	3
26	244
27	5
28	1
29	22
30	21
31	2
32	8
33	7
34	8
35	240
36	7
37	6
38	6
39	4
40	21
41	20
42	4
43	18
44	245
45	8
46	7
47	8
48	4
49	239
50	246
51	20
52	19
53	239
54	5
55	7
56	3
57	12
58	11
59	9
60	8
61	5
62	5
63	468
64	18
65	5
66	4
67	471
68	6
69	239
70	238
71	6
72	5
73	13
74	6
75	471
76	17
77	7
78	6
79	14
80	5
81	468

n	a(n)
1	1
2	2
3	2
4	2
5	2
6	1
7	2
8	2
9	6
10	3
11	245
12	244
13	5
14	4
15	242
16	243
17	5
18	4
19	7
20	6
21	3
22	5
23	242
24	241
25	3
26	244
27	5
28	1
29	22
30	21
31	2
32	8
33	7
34	8
35	240
36	7
37	6
38	6
39	4
40	21
41	20
42	4
43	18
44	245
45	8
46	7
47	8
48	4
49	239
50	246
51	20
52	19
53	239
54	5
55	7
56	3
57	12
58	11
59	9
60	8
61	5
62	5
63	468
64	18
65	5
66	4
67	471
68	6
69	239
70	238
71	6
72	5
73	13
74	6
75	471
76	17
77	7
78	6
79	14
80	5
81	468