A073756 - cp's OEIS frontend

A073756 Number of steps needed to reach a prime when the following map is repeatedly applied to n: if n is even then 2n + floor(log(n)) + 1, otherwise 2n - floor(log(n)) - 1; or -1 if no prime is ever reached.

n	a(n)
2	1
3	3
4	2
5	2
6	2
7	19
8	1
9	19
10	1
11	1
12	18
13	1
14	1
15	18
16	3
17	1
18	12
19	3
20	1
21	9
22	15
23	3
24	8
25	3
26	3
27	17
28	77
29	3
30	5
31	6
32	3
33	9
34	2
35	2
36	2
37	31
38	8
39	11
40	2
41	5
42	2
43	11
44	69
45	34
46	2
47	17
48	14
49	2
50	16
51	33
52	7
53	8
54	2
55	14
56	2
57	1
58	5
59	1
60	76
61	2
62	8
63	5
64	4
65	76
66	1
67	8
68	2
69	4
70	30
71	1
72	1
73	2
74	10
75	30
76	1
77	1
78	4
79	10
80	7
81	1
82	10
83	4
84	1
85	7
86	33
87	10
88	1
89	1
90	16
91	33

[1, 3, 2, 2, 2, 19, 1, 19, 1, 1, 18, 1, 1, 18, 3, 1, 12, 3, 1, 9, 15, 3, 8, 3, 3, 17, 77, 3, 5, 6, 3, 9, 2, 2, 2, 31, 8, 11, 2, 5, 2, 11, 69, 34, 2, 17, 14, 2, 16, 33, 7, 8, 2, 14, 2, 1, 5, 1, 76, 2, 8, 5, 4, 76, 1, 8, 2, 4, 30, 1, 1, 2, 10, 30, 1, 1, 4, 10, 7, 1, 10, 4, 1, 7, 33, 10, 1, 1, 16, 33]

cp's OEIS Frontend

A073756 Number of steps needed to reach a prime when the following map is repeatedly applied to n: if n is even then 2n + floor(log(n)) + 1, otherwise 2n - floor(log(n)) - 1; or -1 if no prime is ever reached.

Table of values

List of values

n	a(n)
2	1
3	3
4	2
5	2
6	2
7	19
8	1
9	19
10	1
11	1
12	18
13	1
14	1
15	18
16	3
17	1
18	12
19	3
20	1
21	9
22	15
23	3
24	8
25	3
26	3
27	17
28	77
29	3
30	5
31	6
32	3
33	9
34	2
35	2
36	2
37	31
38	8
39	11
40	2
41	5
42	2
43	11
44	69
45	34
46	2
47	17
48	14
49	2
50	16
51	33
52	7
53	8
54	2
55	14
56	2
57	1
58	5
59	1
60	76
61	2
62	8
63	5
64	4
65	76
66	1
67	8
68	2
69	4
70	30
71	1
72	1
73	2
74	10
75	30
76	1
77	1
78	4
79	10
80	7
81	1
82	10
83	4
84	1
85	7
86	33
87	10
88	1
89	1
90	16
91	33

n	a(n)
2	1
3	3
4	2
5	2
6	2
7	19
8	1
9	19
10	1
11	1
12	18
13	1
14	1
15	18
16	3
17	1
18	12
19	3
20	1
21	9
22	15
23	3
24	8
25	3
26	3
27	17
28	77
29	3
30	5
31	6
32	3
33	9
34	2
35	2
36	2
37	31
38	8
39	11
40	2
41	5
42	2
43	11
44	69
45	34
46	2
47	17
48	14
49	2
50	16
51	33
52	7
53	8
54	2
55	14
56	2
57	1
58	5
59	1
60	76
61	2
62	8
63	5
64	4
65	76
66	1
67	8
68	2
69	4
70	30
71	1
72	1
73	2
74	10
75	30
76	1
77	1
78	4
79	10
80	7
81	1
82	10
83	4
84	1
85	7
86	33
87	10
88	1
89	1
90	16
91	33

n	a(n)
2	1
3	3
4	2
5	2
6	2
7	19
8	1
9	19
10	1
11	1
12	18
13	1
14	1
15	18
16	3
17	1
18	12
19	3
20	1
21	9
22	15
23	3
24	8
25	3
26	3
27	17
28	77
29	3
30	5
31	6
32	3
33	9
34	2
35	2
36	2
37	31
38	8
39	11
40	2
41	5
42	2
43	11
44	69
45	34
46	2
47	17
48	14
49	2
50	16
51	33
52	7
53	8
54	2
55	14
56	2
57	1
58	5
59	1
60	76
61	2
62	8
63	5
64	4
65	76
66	1
67	8
68	2
69	4
70	30
71	1
72	1
73	2
74	10
75	30
76	1
77	1
78	4
79	10
80	7
81	1
82	10
83	4
84	1
85	7
86	33
87	10
88	1
89	1
90	16
91	33