This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A354183 #11 Jul 07 2022 02:27:51 %S A354183 17,109,151,241,251,257,331,433,631,641,673,683,1321,1429,1459,1613, %T A354183 2917,3191,3457,3889,4733,4861,5153,5419,6337,7001,7351,8581,9719, %U A354183 11119,11251,11471,12101,13367,13553,13669,14323,14449,15121,17539,18503,20231,20857 %N A354183 Primes p such that p divides 2^((p-1)/x) - 1, where x is the greatest prime factor of p - 1. %C A354183 Together with 3 and 5, supersequence of A023394. %C A354183 Are there any odd integers k (k is not a Sierpiński number) such that every prime of the form k*2^m + 1 (m >= 1) does not belong to the sequence? %t A354183 Select[Prime[Range[2500]], PowerMod[2, (# - 1)/FactorInteger[# - 1][[-1, 1]], #] == 1 &] (* _Amiram Eldar_, May 19 2022 *) %o A354183 (Magma) gpf:=func<n | #f eq 0 select 1 else f[#f][1] where f is Factorization(n)>; [p: p in PrimesUpTo(20857) | Modexp(2, Truncate((p-1)/gpf(p-1)), p) eq 1]; %o A354183 (PARI) isok(p) = if (isprime(p) && (p>2), my(x=vecmax(factor(p-1)[,1])); ((2^((p-1)/x) - 1) % p) == 0); \\ _Michel Marcus_, May 19 2022 %Y A354183 Cf. A023394. %K A354183 nonn %O A354183 1,1 %A A354183 _Arkadiusz Wesolowski_, May 18 2022