A367479 - cp's OEIS frontend

A367479 a(n) is the number of steps required for prime(n) to reach 2 when iterating the following hailstone map: If P == 5 (mod 6), then P -> next_prime(P + ceiling(sqrt(P))), otherwise P -> previous_prime(ceiling(sqrt(P))); or a(n) = -1 if prime(n) never reaches 2.

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

[0, 1, 8, 2, 7, 2, 6, 9, 5, 4, 9, 3, 5, 3, 5, 4, 4, 3, 3, 5, 3, 3, 4, 11, 3, 10, 8, 9, 8, 9, 8, 5, 5, 8, 4, 3, 3, 3, 4, 5, 4, 3, 4, 3, 4, 3, 3, 3, 15, 3, 15, 9, 3, 14, 8, 9, 13, 7, 7, 8, 7, 12, 7, 11, 7, 11, 10, 10, 11, 10, 11, 11]

cp's OEIS Frontend

A367479 a(n) is the number of steps required for prime(n) to reach 2 when iterating the following hailstone map: If P == 5 (mod 6), then P -> next_prime(P + ceiling(sqrt(P))), otherwise P -> previous_prime(ceiling(sqrt(P))); or a(n) = -1 if prime(n) never reaches 2.

Table of values

List of values

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

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

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