A188903 - cp's OEIS frontend

A188903 a(n) is the least power of 2 such that 2n+1 - a(n) is prime, or 0 if no such prime exists.

n	a(n)
0	0
1	1
2	2
3	2
4	2
5	4
6	2
7	2
8	4
9	2
10	2
11	4
12	2
13	4
14	16
15	2
16	2
17	4
18	8
19	2
20	4
21	2
22	2
23	4
24	2
25	4
26	16
27	2
28	4
29	16
30	2
31	2
32	4
33	8
34	2
35	4
36	2
37	2
38	4
39	8
40	2
41	4
42	2
43	4
44	16
45	2
46	4
47	16
48	8
49	2
50	4
51	2
52	2
53	4
54	2
55	2
56	4
57	2
58	4
59	16
60	8
61	16
62	16
63	0
64	2
65	4
66	2
67	4
68	64
69	2
70	2
71	4
72	8
73	8
74	0
75	2
76	2
77	4
78	8
79	2
80	4
81	32
82	2
83	4
84	2
85	4
86	16
87	2
88	4
89	16
90	2
91	2
92	4
93	8
94	8
95	64
96	2
97	2
98	4
99	2
100	2
101	4
102	8
103	8
104	16
105	32
106	2
107	4
108	128
109	8
110	64
111	32
112	2
113	4
114	2
115	2
116	4
117	2
118	4
119	16
120	2
121	2
122	4
123	8
124	8
125	0
126	2

[0, 1, 2, 2, 2, 4, 2, 2, 4, 2, 2, 4, 2, 4, 16, 2, 2, 4, 8, 2, 4, 2, 2, 4, 2, 4, 16, 2, 4, 16, 2, 2, 4, 8, 2, 4, 2, 2, 4, 8, 2, 4, 2, 4, 16, 2, 4, 16, 8, 2, 4, 2, 2, 4, 2, 2, 4, 2, 4, 16, 8, 16, 16, 0, 2, 4, 2, 4, 64, 2, 2, 4, 8, 8, 0, 2, 2, 4, 8, 2, 4, 32, 2, 4, 2, 4, 16, 2, 4, 16, 2, 2, 4, 8, 8, 64, 2, 2, 4, 2, 2, 4, 8, 8, 16, 32, 2, 4, 128, 8, 64, 32, 2, 4, 2, 2, 4, 2, 4, 16, 2, 2, 4, 8, 8, 0, 2]

cp's OEIS Frontend

A188903 a(n) is the least power of 2 such that 2n+1 - a(n) is prime, or 0 if no such prime exists.

Table of values

List of values

n	a(n)
0	0
1	1
2	2
3	2
4	2
5	4
6	2
7	2
8	4
9	2
10	2
11	4
12	2
13	4
14	16
15	2
16	2
17	4
18	8
19	2
20	4
21	2
22	2
23	4
24	2
25	4
26	16
27	2
28	4
29	16
30	2
31	2
32	4
33	8
34	2
35	4
36	2
37	2
38	4
39	8
40	2
41	4
42	2
43	4
44	16
45	2
46	4
47	16
48	8
49	2
50	4
51	2
52	2
53	4
54	2
55	2
56	4
57	2
58	4
59	16
60	8
61	16
62	16
63	0
64	2
65	4
66	2
67	4
68	64
69	2
70	2
71	4
72	8
73	8
74	0
75	2
76	2
77	4
78	8
79	2
80	4
81	32
82	2
83	4
84	2
85	4
86	16
87	2
88	4
89	16
90	2
91	2
92	4
93	8
94	8
95	64
96	2
97	2
98	4
99	2
100	2
101	4
102	8
103	8
104	16
105	32
106	2
107	4
108	128
109	8
110	64
111	32
112	2
113	4
114	2
115	2
116	4
117	2
118	4
119	16
120	2
121	2
122	4
123	8
124	8
125	0
126	2

n	a(n)
0	0
1	1
2	2
3	2
4	2
5	4
6	2
7	2
8	4
9	2
10	2
11	4
12	2
13	4
14	16
15	2
16	2
17	4
18	8
19	2
20	4
21	2
22	2
23	4
24	2
25	4
26	16
27	2
28	4
29	16
30	2
31	2
32	4
33	8
34	2
35	4
36	2
37	2
38	4
39	8
40	2
41	4
42	2
43	4
44	16
45	2
46	4
47	16
48	8
49	2
50	4
51	2
52	2
53	4
54	2
55	2
56	4
57	2
58	4
59	16
60	8
61	16
62	16
63	0
64	2
65	4
66	2
67	4
68	64
69	2
70	2
71	4
72	8
73	8
74	0
75	2
76	2
77	4
78	8
79	2
80	4
81	32
82	2
83	4
84	2
85	4
86	16
87	2
88	4
89	16
90	2
91	2
92	4
93	8
94	8
95	64
96	2
97	2
98	4
99	2
100	2
101	4
102	8
103	8
104	16
105	32
106	2
107	4
108	128
109	8
110	64
111	32
112	2
113	4
114	2
115	2
116	4
117	2
118	4
119	16
120	2
121	2
122	4
123	8
124	8
125	0
126	2

n	a(n)
0	0
1	1
2	2
3	2
4	2
5	4
6	2
7	2
8	4
9	2
10	2
11	4
12	2
13	4
14	16
15	2
16	2
17	4
18	8
19	2
20	4
21	2
22	2
23	4
24	2
25	4
26	16
27	2
28	4
29	16
30	2
31	2
32	4
33	8
34	2
35	4
36	2
37	2
38	4
39	8
40	2
41	4
42	2
43	4
44	16
45	2
46	4
47	16
48	8
49	2
50	4
51	2
52	2
53	4
54	2
55	2
56	4
57	2
58	4
59	16
60	8
61	16
62	16
63	0
64	2
65	4
66	2
67	4
68	64
69	2
70	2
71	4
72	8
73	8
74	0
75	2
76	2
77	4
78	8
79	2
80	4
81	32
82	2
83	4
84	2
85	4
86	16
87	2
88	4
89	16
90	2
91	2
92	4
93	8
94	8
95	64
96	2
97	2
98	4
99	2
100	2
101	4
102	8
103	8
104	16
105	32
106	2
107	4
108	128
109	8
110	64
111	32
112	2
113	4
114	2
115	2
116	4
117	2
118	4
119	16
120	2
121	2
122	4
123	8
124	8
125	0
126	2