A339991 - cp's OEIS frontend

A339991 The number of steps that n requires to reach 1 under the map: m -> m/2 if m is even, m-> m^2 - 1 if m is an odd prime, otherwise m -> m - 1. a(n) = -1 if 1 is never reached.

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

[0, 1, 4, 2, 8, 5, 9, 3, 4, 9, 15, 6, 15, 10, 11, 4, 10, 5, 22, 10, 11, 16, 11, 7, 8, 16, 17, 11, 23, 12, 18, 5, 6, 11, 12, 6, 20, 23, 24, 11, 24, 12, 21, 17, 18, 12, 19, 8, 9, 9, 10, 17, 31, 18, 19, 12, 13, 24, 27, 13, 32, 19, 20, 6, 7, 7, 21, 12, 13, 13, 27]

cp's OEIS Frontend

A339991 The number of steps that n requires to reach 1 under the map: m -> m/2 if m is even, m-> m^2 - 1 if m is an odd prime, otherwise m -> m - 1. a(n) = -1 if 1 is never reached.

Table of values

List of values

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

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

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