A057778 - cp's OEIS frontend

A057778 a(n) is the least odd k such that k*2^n + 1 is prime.

n	a(n)
0	1
1	1
2	1
3	5
4	1
5	3
6	3
7	5
8	1
9	15
10	13
11	9
12	3
13	5
14	7
15	5
16	1
17	9
18	3
19	11
20	7
21	11
22	25
23	45
24	45
25	5
26	7
27	15
28	13
29	23
30	3
31	35
32	43
33	9
34	75
35	59
36	3
37	15
38	15
39	5
40	27
41	3
42	9
43	9
44	15
45	35
46	19
47	27
48	15
49	23
50	7
51	17
52	7
53	51
54	49
55	5
56	27
57	29
58	99
59	27
60	31
61	53
62	105
63	9
64	25
65	9
66	3
67	9
68	31
69	23
70	39
71	39
72	127
73	23
74	67
75	5
76	93
77	29
78	15
79	249

[1, 1, 1, 5, 1, 3, 3, 5, 1, 15, 13, 9, 3, 5, 7, 5, 1, 9, 3, 11, 7, 11, 25, 45, 45, 5, 7, 15, 13, 23, 3, 35, 43, 9, 75, 59, 3, 15, 15, 5, 27, 3, 9, 9, 15, 35, 19, 27, 15, 23, 7, 17, 7, 51, 49, 5, 27, 29, 99, 27, 31, 53, 105, 9, 25, 9, 3, 9, 31, 23, 39, 39, 127, 23, 67, 5, 93, 29, 15, 249]

cp's OEIS Frontend

A057778 a(n) is the least odd k such that k*2^n + 1 is prime.

Table of values

List of values

n	a(n)
0	1
1	1
2	1
3	5
4	1
5	3
6	3
7	5
8	1
9	15
10	13
11	9
12	3
13	5
14	7
15	5
16	1
17	9
18	3
19	11
20	7
21	11
22	25
23	45
24	45
25	5
26	7
27	15
28	13
29	23
30	3
31	35
32	43
33	9
34	75
35	59
36	3
37	15
38	15
39	5
40	27
41	3
42	9
43	9
44	15
45	35
46	19
47	27
48	15
49	23
50	7
51	17
52	7
53	51
54	49
55	5
56	27
57	29
58	99
59	27
60	31
61	53
62	105
63	9
64	25
65	9
66	3
67	9
68	31
69	23
70	39
71	39
72	127
73	23
74	67
75	5
76	93
77	29
78	15
79	249

n	a(n)
0	1
1	1
2	1
3	5
4	1
5	3
6	3
7	5
8	1
9	15
10	13
11	9
12	3
13	5
14	7
15	5
16	1
17	9
18	3
19	11
20	7
21	11
22	25
23	45
24	45
25	5
26	7
27	15
28	13
29	23
30	3
31	35
32	43
33	9
34	75
35	59
36	3
37	15
38	15
39	5
40	27
41	3
42	9
43	9
44	15
45	35
46	19
47	27
48	15
49	23
50	7
51	17
52	7
53	51
54	49
55	5
56	27
57	29
58	99
59	27
60	31
61	53
62	105
63	9
64	25
65	9
66	3
67	9
68	31
69	23
70	39
71	39
72	127
73	23
74	67
75	5
76	93
77	29
78	15
79	249

n	a(n)
0	1
1	1
2	1
3	5
4	1
5	3
6	3
7	5
8	1
9	15
10	13
11	9
12	3
13	5
14	7
15	5
16	1
17	9
18	3
19	11
20	7
21	11
22	25
23	45
24	45
25	5
26	7
27	15
28	13
29	23
30	3
31	35
32	43
33	9
34	75
35	59
36	3
37	15
38	15
39	5
40	27
41	3
42	9
43	9
44	15
45	35
46	19
47	27
48	15
49	23
50	7
51	17
52	7
53	51
54	49
55	5
56	27
57	29
58	99
59	27
60	31
61	53
62	105
63	9
64	25
65	9
66	3
67	9
68	31
69	23
70	39
71	39
72	127
73	23
74	67
75	5
76	93
77	29
78	15
79	249