A294658 - cp's OEIS frontend

A294658 Number of steps required to reach either 5 or 13, starting with n, when iterating the map A125256: x -> smallest odd prime divisor of n^2+1; or a(n) = -1 in case 5 is never reached.

n	a(n)
2	1
3	1
4	2
5	0
6	2
7	1
8	1
9	4
10	3
11	5
12	1
13	0
14	2
15	2
16	2
17	1
18	1
19	4
20	3
21	1
22	1
23	1
24	2
25	2
26	2
27	1
28	1
29	2
30	2
31	1
32	1
33	1
34	1
35	2
36	2
37	1
38	1
39	3
40	3
41	3
42	1
43	1
44	1
45	2
46	3
47	1
48	1
49	2
50	4
51	3
52	1
53	1
54	2
55	2
56	2
57	1
58	1
59	4
60	1
61	4
62	1
63	1
64	2
65	2
66	2
67	1
68	1
69	5
70	1
71	3
72	1
73	1
74	2
75	3
76	2
77	1
78	1
79	4
80	2
81	2
82	1
83	1
84	2
85	2
86	1
87	1

[1, 1, 2, 0, 2, 1, 1, 4, 3, 5, 1, 0, 2, 2, 2, 1, 1, 4, 3, 1, 1, 1, 2, 2, 2, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 1, 1, 3, 3, 3, 1, 1, 1, 2, 3, 1, 1, 2, 4, 3, 1, 1, 2, 2, 2, 1, 1, 4, 1, 4, 1, 1, 2, 2, 2, 1, 1, 5, 1, 3, 1, 1, 2, 3, 2, 1, 1, 4, 2, 2, 1, 1, 2, 2, 1, 1]

cp's OEIS Frontend

A294658 Number of steps required to reach either 5 or 13, starting with n, when iterating the map A125256: x -> smallest odd prime divisor of n^2+1; or a(n) = -1 in case 5 is never reached.

Table of values

List of values

n	a(n)
2	1
3	1
4	2
5	0
6	2
7	1
8	1
9	4
10	3
11	5
12	1
13	0
14	2
15	2
16	2
17	1
18	1
19	4
20	3
21	1
22	1
23	1
24	2
25	2
26	2
27	1
28	1
29	2
30	2
31	1
32	1
33	1
34	1
35	2
36	2
37	1
38	1
39	3
40	3
41	3
42	1
43	1
44	1
45	2
46	3
47	1
48	1
49	2
50	4
51	3
52	1
53	1
54	2
55	2
56	2
57	1
58	1
59	4
60	1
61	4
62	1
63	1
64	2
65	2
66	2
67	1
68	1
69	5
70	1
71	3
72	1
73	1
74	2
75	3
76	2
77	1
78	1
79	4
80	2
81	2
82	1
83	1
84	2
85	2
86	1
87	1

n	a(n)
2	1
3	1
4	2
5	0
6	2
7	1
8	1
9	4
10	3
11	5
12	1
13	0
14	2
15	2
16	2
17	1
18	1
19	4
20	3
21	1
22	1
23	1
24	2
25	2
26	2
27	1
28	1
29	2
30	2
31	1
32	1
33	1
34	1
35	2
36	2
37	1
38	1
39	3
40	3
41	3
42	1
43	1
44	1
45	2
46	3
47	1
48	1
49	2
50	4
51	3
52	1
53	1
54	2
55	2
56	2
57	1
58	1
59	4
60	1
61	4
62	1
63	1
64	2
65	2
66	2
67	1
68	1
69	5
70	1
71	3
72	1
73	1
74	2
75	3
76	2
77	1
78	1
79	4
80	2
81	2
82	1
83	1
84	2
85	2
86	1
87	1

n	a(n)
2	1
3	1
4	2
5	0
6	2
7	1
8	1
9	4
10	3
11	5
12	1
13	0
14	2
15	2
16	2
17	1
18	1
19	4
20	3
21	1
22	1
23	1
24	2
25	2
26	2
27	1
28	1
29	2
30	2
31	1
32	1
33	1
34	1
35	2
36	2
37	1
38	1
39	3
40	3
41	3
42	1
43	1
44	1
45	2
46	3
47	1
48	1
49	2
50	4
51	3
52	1
53	1
54	2
55	2
56	2
57	1
58	1
59	4
60	1
61	4
62	1
63	1
64	2
65	2
66	2
67	1
68	1
69	5
70	1
71	3
72	1
73	1
74	2
75	3
76	2
77	1
78	1
79	4
80	2
81	2
82	1
83	1
84	2
85	2
86	1
87	1