A225392 Numbers b such that b^(2^n) + 2 is prime for n from 0 to 4.

22155, 1864149, 2760681, 6222765, 22687797, 25631319, 29309589, 33333069, 36490905, 56310891, 60212889, 74097849, 76008207, 80864685, 84214395, 132006225, 132621171, 137362521, 138993381, 152223885, 154185525, 175950081, 188261481, 188677335, 194279955

Offset: 1

Author

Robin Garcia, May 06 2013

Keywords

• nonn

Comments

Generalized Fermat numbers of the form b^(2^n) + k with k = 2 here.

For b = 2760681, b^(2^n) + 2 is prime for n from 0 to 5

Crossrefs

Cf. A070694, A225321

Programs

PARI

k=2;forstep(b=1,5*10^7,[4,2,2,2],i=0;for(n=0,4,m=b^2^n+k;if(isprime(m),i++;if(i>4,print([b,m,n,i])))))

Extensions

a(10)-a(25) from Giovanni Resta, May 06 2013