A127998 Numbers n such that (24^n - 1)/23 is prime.

3, 5, 19, 53, 71, 653, 661, 10343, 49307, 115597, 152783

Offset: 1

Author

Alexander Adamchuk, Feb 11 2007

Keywords

• hard
• more
• nonn

Comments

Note that 10343 was known to be a term of this sequence before 653 and 661. - Alonso del Arte, Mar 17 2014

Links

• H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.
• Henri Lifchitz, Mersenne and Fermat primes field
• Index to primes in various ranges, form ((k+1)^n-1)/k

Programs

Mathematica

Select[Prime[Range[100]], PrimeQ[(24^# - 1)/23] &]

PARI

isok(n) = isprime((24^n-1)/23); \\ Michel Marcus, Mar 13 2016

Extensions

a(6) and a(7) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008

a(8) from Richard Fischer in 2004.

a(9) from Robert Price, Apr 18 2012

a(10) from Paul Bourdelais, Sep 12 2017

a(11) from Paul Bourdelais, Apr 09 2018