A360781 - cp's OEIS frontend

A360781 Primes p such that at least one number remains prime when p is bracketed by a single digit d; that is, at least one instance of d//p//d is prime where // means concatenation.

n	a(n)
1	2
2	3
3	5
4	7
5	17
6	19
7	23
8	29
9	31
10	37
11	41
12	43
13	47
14	53
15	59
16	61
17	67
18	71
19	73
20	79
21	83
22	101
23	103
24	107
25	109
26	113
27	131
28	139
29	149
30	151
31	157
32	163
33	173
34	179
35	191
36	193
37	197
38	211
39	223
40	227
41	233
42	239
43	241
44	251
45	257
46	263
47	269
48	271
49	277
50	281
51	283
52	293
53	307
54	311
55	313
56	317
57	331

[2, 3, 5, 7, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 101, 103, 107, 109, 113, 131, 139, 149, 151, 157, 163, 173, 179, 191, 193, 197, 211, 223, 227, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331]

cp's OEIS Frontend

A360781 Primes p such that at least one number remains prime when p is bracketed by a single digit d; that is, at least one instance of d//p//d is prime where // means concatenation.

Table of values

List of values

n	a(n)
1	2
2	3
3	5
4	7
5	17
6	19
7	23
8	29
9	31
10	37
11	41
12	43
13	47
14	53
15	59
16	61
17	67
18	71
19	73
20	79
21	83
22	101
23	103
24	107
25	109
26	113
27	131
28	139
29	149
30	151
31	157
32	163
33	173
34	179
35	191
36	193
37	197
38	211
39	223
40	227
41	233
42	239
43	241
44	251
45	257
46	263
47	269
48	271
49	277
50	281
51	283
52	293
53	307
54	311
55	313
56	317
57	331

n	a(n)
1	2
2	3
3	5
4	7
5	17
6	19
7	23
8	29
9	31
10	37
11	41
12	43
13	47
14	53
15	59
16	61
17	67
18	71
19	73
20	79
21	83
22	101
23	103
24	107
25	109
26	113
27	131
28	139
29	149
30	151
31	157
32	163
33	173
34	179
35	191
36	193
37	197
38	211
39	223
40	227
41	233
42	239
43	241
44	251
45	257
46	263
47	269
48	271
49	277
50	281
51	283
52	293
53	307
54	311
55	313
56	317
57	331

n	a(n)
1	2
2	3
3	5
4	7
5	17
6	19
7	23
8	29
9	31
10	37
11	41
12	43
13	47
14	53
15	59
16	61
17	67
18	71
19	73
20	79
21	83
22	101
23	103
24	107
25	109
26	113
27	131
28	139
29	149
30	151
31	157
32	163
33	173
34	179
35	191
36	193
37	197
38	211
39	223
40	227
41	233
42	239
43	241
44	251
45	257
46	263
47	269
48	271
49	277
50	281
51	283
52	293
53	307
54	311
55	313
56	317
57	331