A282946 - OEIS

A282946

Numbers k such that 5*2^k + 1 is a prime factor of a generalized Fermat number 11^(2^m) + 1 for some m.

%I #19 Jan 16 2023 08:10:12

%S 15,1947,125413,240937

%N Numbers k such that 5*2^k + 1 is a prime factor of a generalized Fermat number 11^(2^m) + 1 for some m.

%H Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-98-00891-6">Factors of generalized Fermat numbers</a>, Math. Comp. 67 (1998), no. 221, pp. 441-446.

%H Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-05-01816-8">Table errata to "Factors of generalized Fermat numbers"</a>, Math. Comp. 74 (2005), no. 252, p. 2099.

%H Anders Björn and Hans Riesel, <a href="http://dx.doi.org/10.1090/S0025-5718-10-02371-9">Table errata 2 to "Factors of generalized Fermat numbers"</a>, Math. Comp. 80 (2011), pp. 1865-1866.

%H OEIS Wiki, <a href="/wiki/Generalized_Fermat_numbers">Generalized Fermat numbers</a>

%t lst = {}; Do[p = 5*2^n + 1; If[PrimeQ[p] && IntegerQ@Log[2, MultiplicativeOrder[11, p]], AppendTo[lst, n]], {n, 1, 1947, 2}]; lst

%Y Cf. A199592, A226366, A268661, A268662, A268663, A282945, A268664.

%Y Subsequence of A002254.

%K nonn,hard,more

%O 1,1

%A _Arkadiusz Wesolowski_, Feb 25 2017