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A242797 Numbers n such that (45^n - 1)/44 is prime. 5
19, 53, 167, 3319, 11257, 34351, 216551 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(7) > 10^5.

Numbers corresponding to a(4)-a(6) are probable primes.

All terms are prime.

LINKS

Table of n, a(n) for n=1..7.

Harvey Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.

Henri Lifchitz, Mersenne and Fermat primes field

MAPLE

A242797:=n->`if`(isprime((45^n - 1)/44), n, NULL); seq(A242797(n), n=1..100000); # Wesley Ivan Hurt, Apr 12 2014

MATHEMATICA

Select[Prime[Range[100000]], PrimeQ[(45^# - 1)/44] &]

PROG

(PARI) is(n)=ispseudoprime((45^n-1)/44) \\ Charles R Greathouse IV, Feb 20 2017

CROSSREFS

Cf. A028491, A004061, A004062, A004063, A004023, A005808, A004064, A016054, A006032, A006033, A006034, A006035, A127995, A127996, A127997, A127998, A127999, A098438, A128002, A128003, A128004, A128005, A240765.

Sequence in context: A024848 A240136 A072581 * A142072 A221594 A288144

Adjacent sequences:  A242794 A242795 A242796 * A242798 A242799 A242800

KEYWORD

hard,more,nonn

AUTHOR

Robert Price, May 22 2014

EXTENSIONS

a(7)=216551 corresponds to a probable prime discovered by Paul Bourdelais, Aug 04 2020

STATUS

approved

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Last modified March 2 16:19 EST 2021. Contains 341754 sequences. (Running on oeis4.)