OFFSET
1,1
COMMENTS
Together with 3 and 5, supersequence of A023394.
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?
MATHEMATICA
Select[Prime[Range[2500]], PowerMod[2, (# - 1)/FactorInteger[# - 1][[-1, 1]], #] == 1 &] (* Amiram Eldar, May 19 2022 *)
PROG
(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];
(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
CROSSREFS
KEYWORD
nonn
AUTHOR
Arkadiusz Wesolowski, May 18 2022
STATUS
approved