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A128460 Numbers n such that 19^n - 2 is a prime. 13
1, 2, 3, 13, 14, 19, 20, 23, 38, 1124, 7592, 11755, 12155, 12915, 14172, 15500, 20255, 28388, 184650 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

No more terms through 50000. - Ryan Propper, Dec 04 2008

a(20) > 2*10^5. - Robert Price, Oct 22 2014

LINKS

Table of n, a(n) for n=1..19.

MATHEMATICA

Do[ f = 19^n - 2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n, 1, 1000} ]

PROG

(MAGMA) [n: n in [0..1000] | IsPrime(19^n-2)]; // Vincenzo Librandi, Oct 23 2014

CROSSREFS

Cf. A084714 = smallest prime of the form (2n-1)^k - 2, or 0 if no such number exists. Cf. A128472 = smallest prime of the form (2n-1)^k - 2 for k>(2n-1), or 0 if no such number exists. Cf. A014224, A109080, A090669, A128455, A128457, A128458, A128459, A128461.

Sequence in context: A171483 A100385 A250184 * A273617 A101541 A299543

Adjacent sequences:  A128457 A128458 A128459 * A128461 A128462 A128463

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk, Mar 14 2007

EXTENSIONS

1124 from Stefan Steinerberger, May 05 2007

7592 from Ryan Propper, Dec 31 2007

Additional terms from Ryan Propper, Dec 04 2008

a(19) from Robert Price, Oct 22 2014

STATUS

approved

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Last modified January 25 23:08 EST 2020. Contains 331270 sequences. (Running on oeis4.)