A130139 - cp's OEIS frontend

A130139 Let f denote the map that replaces k with the concatenation of its nontrivial divisors, written in increasing order, each divisor being written in base 10 in the normal way. Then a(n) = prime reached when starting at 2n+1 and iterating f.

n	a(n)
0	1
1	3
2	5
3	7
4	3
5	11
6	13
7	1129
8	17
9	19
10	37
11	23
12	5
13	313
14	29
15	31
16	311
17	1129
18	37
19	313
20	41
21	43

[1, 3, 5, 7, 3, 11, 13, 1129, 17, 19, 37, 23, 5, 313, 29, 31, 311, 1129, 37, 313, 41, 43]