A252168 - cp's OEIS frontend

A252168 Smallest k > 0 such that |(2n-1) - 2^k| is prime, or -1 if no such k exists.

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

[2, 3, 1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 4, 1, 1, 2, 3, 1, 2, 1, 1, 2, 1, 2, 4, 1, 2, 4, 1, 1, 2, 3, 1, 2, 1, 1, 2, 3, 1, 2, 1, 2, 4, 1, 2, 4, 3, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 4, 3, 4, 4, 47, 1, 2, 1, 2, 6, 1, 1, 2, 3, 3, 8, 1, 1, 2, 3, 1, 2, 5, 1, 2, 1, 2, 4]

cp's OEIS Frontend

A252168 Smallest k > 0 such that |(2n-1) - 2^k| is prime, or -1 if no such k exists.

Table of values

List of values

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

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

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