A384713 - cp's OEIS frontend

A384713 The number of steps that n requires to reach 1 under the map: x-> x^2 - 1 if x is an odd prime, x/2 if x is even, x - lpf(x) otherwise where lpf(x) is the least prime factor of x. 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	6
10	9
11	11
12	6
13	12
14	10
15	7
16	4
17	12
18	7
19	14
20	10
21	8
22	12
23	14
24	7
25	11
26	13
27	8
28	11
29	15
30	8
31	14
32	5
33	9
34	13
35	9
36	8
37	16
38	15
39	9
40	11
41	16
42	9
43	17
44	13
45	10
46	15
47	17
48	8
49	10
50	12
51	9
52	14
53	18
54	9
55	13
56	12
57	10
58	16
59	17
60	9
61	19
62	15
63	10
64	6
65	10
66	10
67	20
68	14
69	11
70	10
71	18
72	9
73	20

[0, 1, 4, 2, 8, 5, 9, 3, 6, 9, 11, 6, 12, 10, 7, 4, 12, 7, 14, 10, 8, 12, 14, 7, 11, 13, 8, 11, 15, 8, 14, 5, 9, 13, 9, 8, 16, 15, 9, 11, 16, 9, 17, 13, 10, 15, 17, 8, 10, 12, 9, 14, 18, 9, 13, 12, 10, 16, 17, 9, 19, 15, 10, 6, 10, 10, 20, 14, 11, 10, 18, 9, 20]

cp's OEIS Frontend

A384713 The number of steps that n requires to reach 1 under the map: x-> x^2 - 1 if x is an odd prime, x/2 if x is even, x - lpf(x) otherwise where lpf(x) is the least prime factor of x. 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	6
10	9
11	11
12	6
13	12
14	10
15	7
16	4
17	12
18	7
19	14
20	10
21	8
22	12
23	14
24	7
25	11
26	13
27	8
28	11
29	15
30	8
31	14
32	5
33	9
34	13
35	9
36	8
37	16
38	15
39	9
40	11
41	16
42	9
43	17
44	13
45	10
46	15
47	17
48	8
49	10
50	12
51	9
52	14
53	18
54	9
55	13
56	12
57	10
58	16
59	17
60	9
61	19
62	15
63	10
64	6
65	10
66	10
67	20
68	14
69	11
70	10
71	18
72	9
73	20

n	a(n)
1	0
2	1
3	4
4	2
5	8
6	5
7	9
8	3
9	6
10	9
11	11
12	6
13	12
14	10
15	7
16	4
17	12
18	7
19	14
20	10
21	8
22	12
23	14
24	7
25	11
26	13
27	8
28	11
29	15
30	8
31	14
32	5
33	9
34	13
35	9
36	8
37	16
38	15
39	9
40	11
41	16
42	9
43	17
44	13
45	10
46	15
47	17
48	8
49	10
50	12
51	9
52	14
53	18
54	9
55	13
56	12
57	10
58	16
59	17
60	9
61	19
62	15
63	10
64	6
65	10
66	10
67	20
68	14
69	11
70	10
71	18
72	9
73	20

n	a(n)
1	0
2	1
3	4
4	2
5	8
6	5
7	9
8	3
9	6
10	9
11	11
12	6
13	12
14	10
15	7
16	4
17	12
18	7
19	14
20	10
21	8
22	12
23	14
24	7
25	11
26	13
27	8
28	11
29	15
30	8
31	14
32	5
33	9
34	13
35	9
36	8
37	16
38	15
39	9
40	11
41	16
42	9
43	17
44	13
45	10
46	15
47	17
48	8
49	10
50	12
51	9
52	14
53	18
54	9
55	13
56	12
57	10
58	16
59	17
60	9
61	19
62	15
63	10
64	6
65	10
66	10
67	20
68	14
69	11
70	10
71	18
72	9
73	20