A308438 - cp's OEIS frontend

A308438 a(n) is the smallest prime p whose decimal expansion begins with n and is such that the next prime is p+2n, or -1 if no such prime exists.

n	a(n)
1	11
2	223
3	31
4	401
5	547
6	619
7	773
8	8581
9	9109
10	10223
11	1129
12	12073
13	130553
14	14563
15	150011
16	161471
17	17257
18	18803
19	191189
20	20809
21	210557
22	225383
23	237091
24	240209
25	2509433
26	2613397
27	277429
28	283211
29	2901649
30	308153
31	313409
32	3204139
33	3300613
34	3419063
35	3507739
36	360091
37	3727313
38	3806347
39	3930061
40	4045421
41	41018911

[11, 223, 31, 401, 547, 619, 773, 8581, 9109, 10223, 1129, 12073, 130553, 14563, 150011, 161471, 17257, 18803, 191189, 20809, 210557, 225383, 237091, 240209, 2509433, 2613397, 277429, 283211, 2901649, 308153, 313409, 3204139, 3300613, 3419063, 3507739, 360091, 3727313, 3806347, 3930061, 4045421, 41018911]

cp's OEIS Frontend

A308438 a(n) is the smallest prime p whose decimal expansion begins with n and is such that the next prime is p+2n, or -1 if no such prime exists.

Table of values

List of values