A128004 Numbers n such that (38^n - 1)/37 is prime.

3, 7, 401, 449, 109037

Offset: 1

Author

Alexander Adamchuk, Feb 11 2007

Keywords

• hard
• more
• nonn

Comments

No other terms < 100000. - Robert Price, Dec 23 2011

Links

• H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.
• H. 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[(38^#-1)/37]&]

PARI

is(n)=ispseudoprime((38^n-1)/37) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

a(5) corresponds to a probable prime discovered by Paul Bourdelais, Oct 17 2017