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A239637 Numbers n such that (41^n - 1)/40 is prime. 1
3, 83, 269, 409, 1759, 11731 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 23 22:20 EDT 2019. Contains 326254 sequences. (Running on oeis4.)