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A342660 as a simple table

na(n)
11
23
37
45
531
67
7127
87
913
1031
1119
1231
138191
1431
1531
1673
1773
18127
19131071
2019
2119
2289
23151
24127
25524287
26151
27127
2831
29127
3089
3189
32127
3361
3417
353851
361093
37151
38257
39911
40331
412147483647
423851
43911
44127
45257
461093
47331
48331
49337
50337
51337
52257
53683
543851
558191
561093
57257
58911
593851
601093
61178481
628191
63337
648191

[1,3,7,5,31,7,127,7,13,31,19,31,8191,31,31,73,73,
 127,131071,19,19,89,151,127,524287,151,127,31,127,
 89,89,127,61,17,3851,1093,151,257,911,331,
 2147483647,3851,911,127,257,1093,331,331,337,337,
 337,257,683,3851,8191,1093,257,911,3851,1093,
 178481,8191,337,8191]