A294133 Sorted list of prime factors of numbers of the form 5^(2^m) + 2^(2^m) with m >= 0.

7, 17, 29, 97, 193, 257, 641, 12289, 22993, 65537, 102593, 115201, 152833, 211457, 993793, 5189633, 26411009, 79280897, 93847553, 167772161, 230686721, 1364951041, 1573071713, 3221225473, 5488091137, 186678460417, 206158430209, 274568286337

Offset: 1

Author

Arkadiusz Wesolowski, Oct 23 2017

Keywords

• nonn

Comments

Primes p other than 3 such that the multiplicative order of 5/2 (mod p) is a power of 2.

Links

• Arkadiusz Wesolowski, Table of n, a(n) for n = 1..34
• 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.

Crossrefs

Cf. A094475, A294132, A294134, A294135, A294136.

Programs

PARI

print1(7, ", "); forprime(p=17, 274568286337, z=znorder(Mod(5/2, p)); if(2^ispower(z)==z, print1(p, ", ")));