A257861 - cp's OEIS frontend

A257861 Numbers n such that d(m) - f(m) >= n/2^f(m), where m = 2^n - 1, d(m) is the number of distinct prime factors of m, and f(m) is the number of Fermat primes less than or equal to 65537 that divide m.

%I A257861 #43 Aug 02 2015 17:37:26
%S A257861 24,48,64,72,80,96,112,128,144,160,192,224,240,288,320,336,352,384,
%T A257861 416,448,480,576,672,800,864,960,1056,1440
%N A257861 Numbers n such that d(m) - f(m) >= n/2^f(m), where m = 2^n - 1, d(m) is the number of distinct prime factors of m, and f(m) is the number of Fermat primes less than or equal to 65537 that divide m.
%C A257861 For every n there exists a Sierpiński/Riesel number with modulus a(n).
%H A257861 Wikipedia, <a href="http://en.wikipedia.org/wiki/Covering_set">Covering set</a>
%o A257861 (PARI) lista(nn) = {vfp = [3, 5, 17, 257, 65537]; for(n = 1, nn, m = 2^n-1; dm = omega(m); fm = sum(k=1, #vfp, (m % vfp[k]) == 0); if (dm - fm >= n/2^fm, print1(n, ", ")););} \\ _Michel Marcus_, Jul 20 2015
%Y A257861 Cf. A019434, A046800.
%K A257861 nonn,more
%O A257861 1,1
%A A257861 _Arkadiusz Wesolowski_, Jul 16 2015

cp's OEIS Frontend

A257861 Numbers n such that d(m) - f(m) >= n/2^f(m), where m = 2^n - 1, d(m) is the number of distinct prime factors of m, and f(m) is the number of Fermat primes less than or equal to 65537 that divide m.