A073755 - cp's OEIS frontend

A073755 Number of steps needed to reach a prime when the following map is repeatedly applied to n: if n is even then 2n + int(sqrt(n)) + 1, otherwise 2n - int(sqrt(n)) - 1; or -1 if no prime is ever reached.

n	a(n)
2	10
3	2
4	1
5	1
6	9
7	1
8	1
9	4
10	2
11	2
12	5
13	28
14	3
15	8
16	1
17	1
18	1
19	17
20	2
21	1
22	27
23	1
24	1
25	34
26	7
27	2
28	4
29	12
30	4
31	3
32	2
33	16
34	2
35	2
36	1
37	1
38	1
39	1
40	12
41	4
42	9
43	1
44	33
45	1
46	6
47	12
48	1
49	26
50	2
51	16
52	11
53	5
54	21
55	4
56	2
57	2
58	6
59	8
60	15
61	2
62	3
63	6
64	1
65	11
66	3
67	27
68	2
69	4
70	1
71	15
72	2
73	1
74	1
75	3
76	12
77	2
78	2
79	1
80	8
81	2
82	7
83	3
84	6
85	3
86	16
87	11
88	4
89	2
90	25
91	8
92	4
93	10

[10, 2, 1, 1, 9, 1, 1, 4, 2, 2, 5, 28, 3, 8, 1, 1, 1, 17, 2, 1, 27, 1, 1, 34, 7, 2, 4, 12, 4, 3, 2, 16, 2, 2, 1, 1, 1, 1, 12, 4, 9, 1, 33, 1, 6, 12, 1, 26, 2, 16, 11, 5, 21, 4, 2, 2, 6, 8, 15, 2, 3, 6, 1, 11, 3, 27, 2, 4, 1, 15, 2, 1, 1, 3, 12, 2, 2, 1, 8, 2, 7, 3, 6, 3, 16, 11, 4, 2, 25, 8, 4, 10]

cp's OEIS Frontend

A073755 Number of steps needed to reach a prime when the following map is repeatedly applied to n: if n is even then 2n + int(sqrt(n)) + 1, otherwise 2n - int(sqrt(n)) - 1; or -1 if no prime is ever reached.

Table of values

List of values

n	a(n)
2	10
3	2
4	1
5	1
6	9
7	1
8	1
9	4
10	2
11	2
12	5
13	28
14	3
15	8
16	1
17	1
18	1
19	17
20	2
21	1
22	27
23	1
24	1
25	34
26	7
27	2
28	4
29	12
30	4
31	3
32	2
33	16
34	2
35	2
36	1
37	1
38	1
39	1
40	12
41	4
42	9
43	1
44	33
45	1
46	6
47	12
48	1
49	26
50	2
51	16
52	11
53	5
54	21
55	4
56	2
57	2
58	6
59	8
60	15
61	2
62	3
63	6
64	1
65	11
66	3
67	27
68	2
69	4
70	1
71	15
72	2
73	1
74	1
75	3
76	12
77	2
78	2
79	1
80	8
81	2
82	7
83	3
84	6
85	3
86	16
87	11
88	4
89	2
90	25
91	8
92	4
93	10

n	a(n)
2	10
3	2
4	1
5	1
6	9
7	1
8	1
9	4
10	2
11	2
12	5
13	28
14	3
15	8
16	1
17	1
18	1
19	17
20	2
21	1
22	27
23	1
24	1
25	34
26	7
27	2
28	4
29	12
30	4
31	3
32	2
33	16
34	2
35	2
36	1
37	1
38	1
39	1
40	12
41	4
42	9
43	1
44	33
45	1
46	6
47	12
48	1
49	26
50	2
51	16
52	11
53	5
54	21
55	4
56	2
57	2
58	6
59	8
60	15
61	2
62	3
63	6
64	1
65	11
66	3
67	27
68	2
69	4
70	1
71	15
72	2
73	1
74	1
75	3
76	12
77	2
78	2
79	1
80	8
81	2
82	7
83	3
84	6
85	3
86	16
87	11
88	4
89	2
90	25
91	8
92	4
93	10

n	a(n)
2	10
3	2
4	1
5	1
6	9
7	1
8	1
9	4
10	2
11	2
12	5
13	28
14	3
15	8
16	1
17	1
18	1
19	17
20	2
21	1
22	27
23	1
24	1
25	34
26	7
27	2
28	4
29	12
30	4
31	3
32	2
33	16
34	2
35	2
36	1
37	1
38	1
39	1
40	12
41	4
42	9
43	1
44	33
45	1
46	6
47	12
48	1
49	26
50	2
51	16
52	11
53	5
54	21
55	4
56	2
57	2
58	6
59	8
60	15
61	2
62	3
63	6
64	1
65	11
66	3
67	27
68	2
69	4
70	1
71	15
72	2
73	1
74	1
75	3
76	12
77	2
78	2
79	1
80	8
81	2
82	7
83	3
84	6
85	3
86	16
87	11
88	4
89	2
90	25
91	8
92	4
93	10