A073754 - cp's OEIS frontend

A073754 Number of steps needed to reach a prime when the following map is repeatedly applied to n: if n is even then 2n + #(n) + 1, otherwise 2n - #(n) - 1, where #(n) is the number of digits of n; or -1 is no prime is ever reached.

n	a(n)
2	3
3	3
4	2
5	12
6	2
7	10
8	11
9	3
10	1
11	1
12	9
13	1
14	1
15	9
16	2
17	1
18	10
19	2
20	1
21	10
22	1
23	1
24	8
25	1
26	2
27	8
28	1
29	2
30	13
31	1
32	1
33	13
34	1
35	1
36	9
37	1
38	1
39	9
40	1
41	1
42	35
43	1
44	2
45	35
46	8
47	2
48	7
49	8
50	1
51	7
52	1
53	1
54	52
55	1
56	6
57	52
58	21
59	6
60	12
61	21
62	1
63	12
64	1
65	1
66	12
67	1
68	1
69	12
70	28
71	1
72	8
73	28
74	1
75	8
76	5
77	1
78	6
79	5
80	1
81	6
82	1
83	1
84	34
85	1
86	5
87	34
88	1
89	5
90	71
91	1
92	7

[3, 3, 2, 12, 2, 10, 11, 3, 1, 1, 9, 1, 1, 9, 2, 1, 10, 2, 1, 10, 1, 1, 8, 1, 2, 8, 1, 2, 13, 1, 1, 13, 1, 1, 9, 1, 1, 9, 1, 1, 35, 1, 2, 35, 8, 2, 7, 8, 1, 7, 1, 1, 52, 1, 6, 52, 21, 6, 12, 21, 1, 12, 1, 1, 12, 1, 1, 12, 28, 1, 8, 28, 1, 8, 5, 1, 6, 5, 1, 6, 1, 1, 34, 1, 5, 34, 1, 5, 71, 1, 7]

cp's OEIS Frontend

A073754 Number of steps needed to reach a prime when the following map is repeatedly applied to n: if n is even then 2n + #(n) + 1, otherwise 2n - #(n) - 1, where #(n) is the number of digits of n; or -1 is no prime is ever reached.

Table of values

List of values

n	a(n)
2	3
3	3
4	2
5	12
6	2
7	10
8	11
9	3
10	1
11	1
12	9
13	1
14	1
15	9
16	2
17	1
18	10
19	2
20	1
21	10
22	1
23	1
24	8
25	1
26	2
27	8
28	1
29	2
30	13
31	1
32	1
33	13
34	1
35	1
36	9
37	1
38	1
39	9
40	1
41	1
42	35
43	1
44	2
45	35
46	8
47	2
48	7
49	8
50	1
51	7
52	1
53	1
54	52
55	1
56	6
57	52
58	21
59	6
60	12
61	21
62	1
63	12
64	1
65	1
66	12
67	1
68	1
69	12
70	28
71	1
72	8
73	28
74	1
75	8
76	5
77	1
78	6
79	5
80	1
81	6
82	1
83	1
84	34
85	1
86	5
87	34
88	1
89	5
90	71
91	1
92	7

n	a(n)
2	3
3	3
4	2
5	12
6	2
7	10
8	11
9	3
10	1
11	1
12	9
13	1
14	1
15	9
16	2
17	1
18	10
19	2
20	1
21	10
22	1
23	1
24	8
25	1
26	2
27	8
28	1
29	2
30	13
31	1
32	1
33	13
34	1
35	1
36	9
37	1
38	1
39	9
40	1
41	1
42	35
43	1
44	2
45	35
46	8
47	2
48	7
49	8
50	1
51	7
52	1
53	1
54	52
55	1
56	6
57	52
58	21
59	6
60	12
61	21
62	1
63	12
64	1
65	1
66	12
67	1
68	1
69	12
70	28
71	1
72	8
73	28
74	1
75	8
76	5
77	1
78	6
79	5
80	1
81	6
82	1
83	1
84	34
85	1
86	5
87	34
88	1
89	5
90	71
91	1
92	7

n	a(n)
2	3
3	3
4	2
5	12
6	2
7	10
8	11
9	3
10	1
11	1
12	9
13	1
14	1
15	9
16	2
17	1
18	10
19	2
20	1
21	10
22	1
23	1
24	8
25	1
26	2
27	8
28	1
29	2
30	13
31	1
32	1
33	13
34	1
35	1
36	9
37	1
38	1
39	9
40	1
41	1
42	35
43	1
44	2
45	35
46	8
47	2
48	7
49	8
50	1
51	7
52	1
53	1
54	52
55	1
56	6
57	52
58	21
59	6
60	12
61	21
62	1
63	12
64	1
65	1
66	12
67	1
68	1
69	12
70	28
71	1
72	8
73	28
74	1
75	8
76	5
77	1
78	6
79	5
80	1
81	6
82	1
83	1
84	34
85	1
86	5
87	34
88	1
89	5
90	71
91	1
92	7