A040081 - cp's OEIS frontend

A040081 Riesel problem: a(n) = smallest m >= 0 such that n*2^m-1 is prime, or -1 if no such prime exists.

n	a(n)
1	2
2	1
3	0
4	0
5	2
6	0
7	1
8	0
9	1
10	1
11	2
12	0
13	3
14	0
15	1
16	1
17	2
18	0
19	1
20	0
21	1
22	1
23	4
24	0
25	3
26	2
27	1
28	3
29	4
30	0
31	1
32	0
33	2
34	1
35	2
36	1
37	1
38	0
39	3
40	1
41	2
42	0
43	7
44	0
45	1
46	3
47	4
48	0
49	1
50	2
51	1
52	1
53	2
54	0
55	1
56	2
57	1
58	3
59	12
60	0
61	3
62	0
63	2
64	1
65	4
66	1
67	5
68	0
69	1
70	1
71	2
72	0
73	7
74	0
75	1
76	1
77	2
78	2
79	1
80	0
81	3
82	1
83	2
84	0
85	5
86	6
87	1
88	23
89	4
90	0
91	1
92	2
93	3
94	3
95	2
96	1
97	1
98	0
99	1
100	1
101	10
102	0
103	3

[2, 1, 0, 0, 2, 0, 1, 0, 1, 1, 2, 0, 3, 0, 1, 1, 2, 0, 1, 0, 1, 1, 4, 0, 3, 2, 1, 3, 4, 0, 1, 0, 2, 1, 2, 1, 1, 0, 3, 1, 2, 0, 7, 0, 1, 3, 4, 0, 1, 2, 1, 1, 2, 0, 1, 2, 1, 3, 12, 0, 3, 0, 2, 1, 4, 1, 5, 0, 1, 1, 2, 0, 7, 0, 1, 1, 2, 2, 1, 0, 3, 1, 2, 0, 5, 6, 1, 23, 4, 0, 1, 2, 3, 3, 2, 1, 1, 0, 1, 1, 10, 0, 3]

cp's OEIS Frontend

A040081 Riesel problem: a(n) = smallest m >= 0 such that n*2^m-1 is prime, or -1 if no such prime exists.

Table of values

List of values

n	a(n)
1	2
2	1
3	0
4	0
5	2
6	0
7	1
8	0
9	1
10	1
11	2
12	0
13	3
14	0
15	1
16	1
17	2
18	0
19	1
20	0
21	1
22	1
23	4
24	0
25	3
26	2
27	1
28	3
29	4
30	0
31	1
32	0
33	2
34	1
35	2
36	1
37	1
38	0
39	3
40	1
41	2
42	0
43	7
44	0
45	1
46	3
47	4
48	0
49	1
50	2
51	1
52	1
53	2
54	0
55	1
56	2
57	1
58	3
59	12
60	0
61	3
62	0
63	2
64	1
65	4
66	1
67	5
68	0
69	1
70	1
71	2
72	0
73	7
74	0
75	1
76	1
77	2
78	2
79	1
80	0
81	3
82	1
83	2
84	0
85	5
86	6
87	1
88	23
89	4
90	0
91	1
92	2
93	3
94	3
95	2
96	1
97	1
98	0
99	1
100	1
101	10
102	0
103	3

n	a(n)
1	2
2	1
3	0
4	0
5	2
6	0
7	1
8	0
9	1
10	1
11	2
12	0
13	3
14	0
15	1
16	1
17	2
18	0
19	1
20	0
21	1
22	1
23	4
24	0
25	3
26	2
27	1
28	3
29	4
30	0
31	1
32	0
33	2
34	1
35	2
36	1
37	1
38	0
39	3
40	1
41	2
42	0
43	7
44	0
45	1
46	3
47	4
48	0
49	1
50	2
51	1
52	1
53	2
54	0
55	1
56	2
57	1
58	3
59	12
60	0
61	3
62	0
63	2
64	1
65	4
66	1
67	5
68	0
69	1
70	1
71	2
72	0
73	7
74	0
75	1
76	1
77	2
78	2
79	1
80	0
81	3
82	1
83	2
84	0
85	5
86	6
87	1
88	23
89	4
90	0
91	1
92	2
93	3
94	3
95	2
96	1
97	1
98	0
99	1
100	1
101	10
102	0
103	3

n	a(n)
1	2
2	1
3	0
4	0
5	2
6	0
7	1
8	0
9	1
10	1
11	2
12	0
13	3
14	0
15	1
16	1
17	2
18	0
19	1
20	0
21	1
22	1
23	4
24	0
25	3
26	2
27	1
28	3
29	4
30	0
31	1
32	0
33	2
34	1
35	2
36	1
37	1
38	0
39	3
40	1
41	2
42	0
43	7
44	0
45	1
46	3
47	4
48	0
49	1
50	2
51	1
52	1
53	2
54	0
55	1
56	2
57	1
58	3
59	12
60	0
61	3
62	0
63	2
64	1
65	4
66	1
67	5
68	0
69	1
70	1
71	2
72	0
73	7
74	0
75	1
76	1
77	2
78	2
79	1
80	0
81	3
82	1
83	2
84	0
85	5
86	6
87	1
88	23
89	4
90	0
91	1
92	2
93	3
94	3
95	2
96	1
97	1
98	0
99	1
100	1
101	10
102	0
103	3