A067849 - cp's OEIS frontend

A067849 a(n) = max{k: f(n),...,f^k(n) are prime}, where f(m) = 2m+1 and f^k denotes composition of f with itself k times.

n	a(n)
1	2
2	4
3	1
4	0
5	3
6	1
7	0
8	1
9	1
10	0
11	2
12	0
13	0
14	2
15	1
16	0
17	0
18	1
19	0
20	3
21	1
22	0
23	1
24	0
25	0
26	2
27	0
28	0
29	1
30	1
31	0
32	0
33	1
34	0
35	1
36	1
37	0
38	0
39	1
40	0
41	2
42	0
43	0
44	6
45	0
46	0
47	0
48	1
49	0
50	1
51	1
52	0
53	1
54	1
55	0
56	2
57	0
58	0
59	0
60	0
61	0
62	0
63	1
64	0
65	2
66	0
67	0
68	1
69	1
70	0
71	0
72	0
73	0
74	1
75	1
76	0
77	0
78	1
79	0
80	0
81	1
82	0
83	1
84	0
85	0
86	2
87	0
88	0
89	5
90	1

[2, 4, 1, 0, 3, 1, 0, 1, 1, 0, 2, 0, 0, 2, 1, 0, 0, 1, 0, 3, 1, 0, 1, 0, 0, 2, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 2, 0, 0, 6, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 2, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 2, 0, 0, 5, 1]

cp's OEIS Frontend

A067849 a(n) = max{k: f(n),...,f^k(n) are prime}, where f(m) = 2m+1 and f^k denotes composition of f with itself k times.

Table of values

List of values

n	a(n)
1	2
2	4
3	1
4	0
5	3
6	1
7	0
8	1
9	1
10	0
11	2
12	0
13	0
14	2
15	1
16	0
17	0
18	1
19	0
20	3
21	1
22	0
23	1
24	0
25	0
26	2
27	0
28	0
29	1
30	1
31	0
32	0
33	1
34	0
35	1
36	1
37	0
38	0
39	1
40	0
41	2
42	0
43	0
44	6
45	0
46	0
47	0
48	1
49	0
50	1
51	1
52	0
53	1
54	1
55	0
56	2
57	0
58	0
59	0
60	0
61	0
62	0
63	1
64	0
65	2
66	0
67	0
68	1
69	1
70	0
71	0
72	0
73	0
74	1
75	1
76	0
77	0
78	1
79	0
80	0
81	1
82	0
83	1
84	0
85	0
86	2
87	0
88	0
89	5
90	1

n	a(n)
1	2
2	4
3	1
4	0
5	3
6	1
7	0
8	1
9	1
10	0
11	2
12	0
13	0
14	2
15	1
16	0
17	0
18	1
19	0
20	3
21	1
22	0
23	1
24	0
25	0
26	2
27	0
28	0
29	1
30	1
31	0
32	0
33	1
34	0
35	1
36	1
37	0
38	0
39	1
40	0
41	2
42	0
43	0
44	6
45	0
46	0
47	0
48	1
49	0
50	1
51	1
52	0
53	1
54	1
55	0
56	2
57	0
58	0
59	0
60	0
61	0
62	0
63	1
64	0
65	2
66	0
67	0
68	1
69	1
70	0
71	0
72	0
73	0
74	1
75	1
76	0
77	0
78	1
79	0
80	0
81	1
82	0
83	1
84	0
85	0
86	2
87	0
88	0
89	5
90	1

n	a(n)
1	2
2	4
3	1
4	0
5	3
6	1
7	0
8	1
9	1
10	0
11	2
12	0
13	0
14	2
15	1
16	0
17	0
18	1
19	0
20	3
21	1
22	0
23	1
24	0
25	0
26	2
27	0
28	0
29	1
30	1
31	0
32	0
33	1
34	0
35	1
36	1
37	0
38	0
39	1
40	0
41	2
42	0
43	0
44	6
45	0
46	0
47	0
48	1
49	0
50	1
51	1
52	0
53	1
54	1
55	0
56	2
57	0
58	0
59	0
60	0
61	0
62	0
63	1
64	0
65	2
66	0
67	0
68	1
69	1
70	0
71	0
72	0
73	0
74	1
75	1
76	0
77	0
78	1
79	0
80	0
81	1
82	0
83	1
84	0
85	0
86	2
87	0
88	0
89	5
90	1