A057187 Numbers n such that (21^n+1)/22 is a prime.

3, 5, 7, 13, 37, 347, 17597, 59183, 80761, 210599, 394579

Offset: 1

Author

N. J. A. Sloane, Sep 15 2000

Keywords

• nonn

Comments

Some of the larger terms correspond to probable primes.

Links

• 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]

Programs

Prime95

PRP=1,21,394579,1,0,0,"22"

Extensions

a(7) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008

a(8) corresponds to a probable prime discovered by Paul Bourdelais, Mar 22 2010

a(9) corresponds to a probable prime discovered by Paul Bourdelais, Mar 24 2010

a(10) corresponds to a probable prime discovered by Paul Bourdelais, Aug 30 2013

a(11) corresponds to a probable prime discovered by Paul Bourdelais, Oct 23 2018