A392504 - OEIS

A392504 as a simple table

n	a(n)
1	-1
2	-1
3	-1
4	-1
5	1111111111111111111
6	31
7	71
8	191
9	223
10	229
11	13
12	73
13	4111
14	433
15	4447
16	353
17	599
18	661
19	677
20	17
21	37
22	97
23	383
24	8999
25	79
26	10111
27	1013
28	701
29	1009
30	13
31	271
32	13
33	173
34	193
35	419
36	1151
37	571
38	613
39	617
40	137
41	197
42	811
43	19
44	139
45	179
46	19
47	2111
48	23
49	277
50	29
51	23
52	293
53	421
54	521
55	2557

[-1,-1,-1,-1,1111111111111111111,31,71,191,223, 229,13,73,4111,433,4447,353,599,661,677,17,37,97, 383,8999,79,10111,1013,701,1009,13,271,13,173,193, 419,1151,571,613,617,137,197,811,19,139,179,19, 2111,23,277,29,23,293,421,521,2557]