

A128000


Numbers n such that (28^n  1)/27 is prime.


2




OFFSET

1,1


COMMENTS

No other terms less than 100000.  Robert Price, May 01 2012


LINKS

Table of n, a(n) for n=1..6.
H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927930.
H. Lifchitz, Mersenne and Fermat primes field
Index to primes in various ranges, form ((k+1)^n1)/k


MATHEMATICA

Select[Prime[Range[100]], PrimeQ[(28^#1)/27]&]


PROG

(PARI) is(n)=ispseudoprime((28^n1)/27) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Sequence in context: A111635 A041455 A081465 * A281312 A182313 A124374
Adjacent sequences: A127997 A127998 A127999 * A128001 A128002 A128003


KEYWORD

hard,more,nonn


AUTHOR

Alexander Adamchuk, Feb 11 2007


EXTENSIONS

1423 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008
a(6)=115877 corresponds to a probable prime discovered by Paul Bourdelais, Dec 08 2017


STATUS

approved



