A178723 Pseudoprimes to base 2 of the form 4k+1.

341, 561, 645, 1105, 1729, 1905, 2465, 2701, 2821, 3277, 4033, 4369, 4681, 5461, 6601, 7957, 8321, 8481, 10261, 10585, 11305, 12801, 13741, 13981, 15709, 15841, 16705, 18705, 18721, 23001, 23377, 25761, 29341, 30121, 30889, 31417, 31609, 31621, 33153, 34945, 35333, 39865, 41041, 41665, 46657, 49141, 49981, 52633

Offset: 1

Author

Joerg Arndt, Dec 30 2010

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001567, A177884.

Programs

Mathematica

Select[4 * Range[10^4] + 1, CompositeQ[#] && PowerMod[2, # - 1, #] == 1 &] (* Amiram Eldar, Sep 10 2019 *)

PARI

forstep(n=5, 10^7, 4, if(isprime(n), next()); if(Mod(2, n)^(n-1)==1, print1(n, ", ")))