

A057187


Numbers n such that (21^n+1)/22 is a prime.


13




OFFSET

1,1


COMMENTS

Some of the larger terms may only correspond to probable primes.
Searching to n=100000. [From Paul Bourdelais, Mar 24 2010]


LINKS

Table of n, a(n) for n=1..10.
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
H. Lifchitz, Mersenne and Fermat primes field
Paul Bourdelais,A Generalized Repunit Conjecture [From Paul Bourdelais, Mar 24 2010]


PROG

(Prime95) PRP=1, 21, 210599, 1, 0, 0, "22"


CROSSREFS

Sequence in context: A047933 A075557 A244452 * A163080 A141414 A236464
Adjacent sequences: A057184 A057185 A057186 * A057188 A057189 A057190


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, Sep 15 2000


EXTENSIONS

17597 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008
a(8)=59183 is a probable prime discovered by Paul Bourdelais, Mar 22 2010
a(9)=80761 is a probable prime discovered by Paul Bourdelais, Mar 24 2010
a(10)=210599 is a probable prime discovered by Paul Bourdelais, Aug 30 2013


STATUS

approved



