A239637 Numbers n such that (41^n - 1)/40 is prime.

3, 83, 269, 409, 1759, 11731

Offset

1,1

Comments

a(7) > 10^5. - Robert Price, Mar 22 2014

Links

Table of n, a(n) for n=1..6.

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

Mathematica

Select[Prime[Range[100000]], PrimeQ[(41^#-1)/40]&]

Prog

(PARI) isok(n) = isprime((41^n-1)/40); \\ Michel Marcus, Mar 13 2016

Crossrefs

Sequence in context: A085318 A101717 A053974 * A201963 A261434 A020464

Adjacent sequences: A239634 A239635 A239636 * A239638 A239639 A239640

Keyword

hard,more,nonn

Author

Robert Price, Mar 22 2014

Status

approved