A213187 - cp's OEIS frontend

A213187 a(n) = (p+1)/2 if 4 | p+1, and p otherwise, where p is the least prime > n with 2(n+1)-p prime.

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

[2, 2, 5, 5, 4, 4, 6, 6, 13, 6, 13, 13, 17, 17, 10, 17, 10, 10, 12, 12, 16, 12, 29, 16, 29, 16, 37, 29, 16, 16, 41, 37, 37, 41, 41, 37, 24, 41, 22, 41, 22, 22, 24, 24, 61, 24, 53, 61, 53, 30, 61, 53, 61, 34, 30, 61, 73, 30, 61, 61, 36, 34, 34, 36, 36, 34, 42, 36, 73, 36, 73, 73, 89, 40, 40, 42, 42, 40, 89, 42, 97, 42, 89, 97, 89, 101, 97, 89, 97, 52, 101, 97, 109, 101, 52, 97, 54, 101, 52, 101]

cp's OEIS Frontend

A213187 a(n) = (p+1)/2 if 4 | p+1, and p otherwise, where p is the least prime > n with 2(n+1)-p prime.

Table of values

List of values

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

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

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