A305473 - cp's OEIS frontend

A305473 Let k be a Sierpiński or Riesel number divisible by 2n - 1, and let p be the largest number in a set of primes which cover every number of the form k2^m + 1 (or of the form k*2^m - 1) with m >= 1. a(n) = p if and only if there exists no number k that has a covering set with largest prime < p.

n	a(n)
1	73
2	257
3	151
4	151
5	257
6	73
7	151
8	1321
9	73
10	109
11	1321
12	73
13	151
14	257
15	73
16	73
17	331
18	257
19	109
20	331
21	73
22	73
23	1321
24	73
25	151
26	331
27	73
28	241

[73, 257, 151, 151, 257, 73, 151, 1321, 73, 109, 1321, 73, 151, 257, 73, 73, 331, 257, 109, 331, 73, 73, 1321, 73, 151, 331, 73, 241]