A111475 - cp's OEIS frontend

A111475 a(1) = 7, a(n) = least k such that concatenation of n copies of k with all previous concatenation gives a prime.

n	a(n)
1	7
2	3
3	1
4	1
5	1
6	1
7	129
8	123
9	97
10	559
11	781
12	459
13	253
14	183
15	413
16	417
17	657
18	77
19	437
20	1439
21	667
22	1281
23	3379
24	979
25	2763
26	1953
27	103
28	10083
29	5103
30	291
31	1311
32	2199
33	1159
34	501
35	5931
36	483
37	6171
38	16301
39	1781
40	1229
41	9519
42	607
43	5113
44	2641
45	1441
46	8511
47	9023
48	363
49	4001
50	15261

[7, 3, 1, 1, 1, 1, 129, 123, 97, 559, 781, 459, 253, 183, 413, 417, 657, 77, 437, 1439, 667, 1281, 3379, 979, 2763, 1953, 103, 10083, 5103, 291, 1311, 2199, 1159, 501, 5931, 483, 6171, 16301, 1781, 1229, 9519, 607, 5113, 2641, 1441, 8511, 9023, 363, 4001, 15261]

cp's OEIS Frontend

A111475 a(1) = 7, a(n) = least k such that concatenation of n copies of k with all previous concatenation gives a prime.

Table of values

List of values