A345223 - cp's OEIS frontend

A345223 a(n) is the smallest k >= 0 such that the decimal concatenation 1 (n times) || k || 1 (n times) is a prime, or -1 if no such k exists.

n	a(n)
1	0
2	3
3	4
4	8
5	10
6	8
7	5
8	21
9	1
10	6
11	1
12	116
13	23
14	6
15	73
16	24
17	16
18	62
19	3
20	10
21	19
22	53
23	61
24	58
25	191
26	9
27	265
28	12
29	133
30	86
31	141
32	4
33	7
34	39
35	193
36	31
37	51
38	13
39	31
40	6
41	31
42	53
43	287
44	139
45	4
46	239
47	187
48	25
49	18
50	144
51	31
52	38
53	93
54	86
55	27
56	30
57	16
58	24
59	6
60	356
61	50
62	91
63	395
64	117
65	217
66	61

[0, 3, 4, 8, 10, 8, 5, 21, 1, 6, 1, 116, 23, 6, 73, 24, 16, 62, 3, 10, 19, 53, 61, 58, 191, 9, 265, 12, 133, 86, 141, 4, 7, 39, 193, 31, 51, 13, 31, 6, 31, 53, 287, 139, 4, 239, 187, 25, 18, 144, 31, 38, 93, 86, 27, 30, 16, 24, 6, 356, 50, 91, 395, 117, 217, 61]

cp's OEIS Frontend

A345223 a(n) is the smallest k >= 0 such that the decimal concatenation 1 (n times) || k || 1 (n times) is a prime, or -1 if no such k exists.

Table of values

List of values

n	a(n)
1	0
2	3
3	4
4	8
5	10
6	8
7	5
8	21
9	1
10	6
11	1
12	116
13	23
14	6
15	73
16	24
17	16
18	62
19	3
20	10
21	19
22	53
23	61
24	58
25	191
26	9
27	265
28	12
29	133
30	86
31	141
32	4
33	7
34	39
35	193
36	31
37	51
38	13
39	31
40	6
41	31
42	53
43	287
44	139
45	4
46	239
47	187
48	25
49	18
50	144
51	31
52	38
53	93
54	86
55	27
56	30
57	16
58	24
59	6
60	356
61	50
62	91
63	395
64	117
65	217
66	61

n	a(n)
1	0
2	3
3	4
4	8
5	10
6	8
7	5
8	21
9	1
10	6
11	1
12	116
13	23
14	6
15	73
16	24
17	16
18	62
19	3
20	10
21	19
22	53
23	61
24	58
25	191
26	9
27	265
28	12
29	133
30	86
31	141
32	4
33	7
34	39
35	193
36	31
37	51
38	13
39	31
40	6
41	31
42	53
43	287
44	139
45	4
46	239
47	187
48	25
49	18
50	144
51	31
52	38
53	93
54	86
55	27
56	30
57	16
58	24
59	6
60	356
61	50
62	91
63	395
64	117
65	217
66	61

n	a(n)
1	0
2	3
3	4
4	8
5	10
6	8
7	5
8	21
9	1
10	6
11	1
12	116
13	23
14	6
15	73
16	24
17	16
18	62
19	3
20	10
21	19
22	53
23	61
24	58
25	191
26	9
27	265
28	12
29	133
30	86
31	141
32	4
33	7
34	39
35	193
36	31
37	51
38	13
39	31
40	6
41	31
42	53
43	287
44	139
45	4
46	239
47	187
48	25
49	18
50	144
51	31
52	38
53	93
54	86
55	27
56	30
57	16
58	24
59	6
60	356
61	50
62	91
63	395
64	117
65	217
66	61