A282945 Numbers k such that 5*2^k + 1 is a prime factor of a generalized Fermat number 7^(2^m) + 1 for some m.

15, 13165, 23473, 1777515

Offset: 1

Author

Arkadiusz Wesolowski, Feb 25 2017

Keywords

• nonn
• hard
• more

Links

• Anders Björn and Hans Riesel, Factors of generalized Fermat numbers, Math. Comp. 67 (1998), no. 221, pp. 441-446.
• Anders Björn and Hans Riesel, Table errata to "Factors of generalized Fermat numbers", Math. Comp. 74 (2005), no. 252, p. 2099.
• Anders Björn and Hans Riesel, Table errata 2 to "Factors of generalized Fermat numbers", Math. Comp. 80 (2011), pp. 1865-1866.
• OEIS Wiki, Generalized Fermat numbers

Crossrefs

Cf. A078304, A226366, A268661, A268662, A268663, A282946, A268664.

Subsequence of A002254.

Programs

Mathematica

lst = {}; Do[p = 5*2^n + 1; If[PrimeQ[p] && IntegerQ@Log[2, MultiplicativeOrder[7, p]], AppendTo[lst, n]], {n, 1, 13165, 2}]; lst