A231557 - cp's OEIS frontend

A231557 Least positive integer k <= n such that 2^k + (n - k) is prime, or 0 if such an integer k does not exist.

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

[1, 1, 2, 1, 2, 1, 4, 3, 2, 1, 2, 1, 6, 3, 2, 1, 2, 1, 4, 5, 2, 1, 8, 3, 4, 3, 2, 1, 2, 1, 4, 3, 8, 5, 2, 1, 10, 3, 2, 1, 2, 1, 6, 5, 2, 1, 4, 3, 4, 11, 2, 1, 20, 3, 4, 3, 2, 1, 2, 1, 4, 3, 8, 13, 2, 1, 4, 3, 2, 1, 2, 1, 6, 3, 12, 5, 2, 1, 6, 5, 2, 1, 8, 3, 4, 5, 2, 1, 4, 7, 4, 3, 6, 11, 2, 1, 4, 3, 2, 1]

cp's OEIS Frontend

A231557 Least positive integer k <= n such that 2^k + (n - k) is prime, or 0 if such an integer k does not exist.

Table of values

List of values

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

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

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