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Primes p (A000043) such that 2^p-1 is prime (A000668) and congruent to 271 mod 6!.
4

%I #18 Sep 04 2023 15:27:20

%S 13,61,2281,3217,23209,44497,132049,13466917,30402457,42643801

%N Primes p (A000043) such that 2^p-1 is prime (A000668) and congruent to 271 mod 6!.

%C Mersenne numbers (with the exception of the first two) are congruent to 31, 127, 271, 607 mod 6!. This sequence is a subsequence of A000043.

%t Select[MersennePrimeExponent[Range[47]], PowerMod[2, #, 6!] == 272 &] (* _Amiram Eldar_, Mar 22 2020 *)

%Y Cf. A000043, A000668, A124477, A139484, A145038, A112633, A145041, A145042, A145044, A145045, A145046.

%K nonn,more

%O 1,1

%A _Artur Jasinski_, Sep 30 2008

%E a(10) from _Amiram Eldar_, Mar 22 2020