

A128002


Numbers n such that (31^n  1)/30 is prime.


9




OFFSET

1,1


COMMENTS

9973 is a term found by Richard Fischer in 2004.  Alexander Adamchuk, Feb 11 2007
No other terms < 101833.  Robert Price, Nov 26 2011


LINKS

Table of n, a(n) for n=1..7.
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[(31^#1)/30]&]


PROG

(PARI) is(n)=ispseudoprime((31^n1)/30) \\ Charles R Greathouse IV, Feb 17 2017


CROSSREFS

Sequence in context: A319304 A144861 A066436 * A301695 A301725 A278920
Adjacent sequences: A127999 A128000 A128001 * A128003 A128004 A128005


KEYWORD

hard,more,nonn


AUTHOR

Alexander Adamchuk, Feb 11 2007


EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008
a(6) = 101111 by Robert Price, Nov 26 2011
a(7) = 535571 from Alexander Zhirkov, added by Paul Bourdelais, Jan 28 2021


STATUS

approved



