

A098438


Numbers k such that (30^k  1)/29 is prime.


10




OFFSET

1,1


COMMENTS

No other terms < 10^5.  Robert Price


LINKS

Table of n, a(n) for n=1..10.
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

Do[If[PrimeQ[(30^n  1)/29], Print[n]], {n, 1, 10000}] (* Ryan Propper, Jun 25 2005 *)
Select[Prime[Range[100]], PrimeQ[(30^#1)/29]&] (* Alexander Adamchuk, Feb 11 2007 *)


PROG

(MAGMA) for i in [1..500] do if i mod 50 eq 0 then print "counter equals", counter; end if; if IsPrime(i) then n := 0; for j in [0..i1] do n +:= 30^j; end for; if IsPrime(n) then print n; print i; end if; end if; end for;
(PARI) is(n)=n=(30^n1)/29; denominator(n)==1&&ispseudoprime(n) \\ Charles R Greathouse IV, Jul 01 2013


CROSSREFS

Searching in the OEIS for 'repunit' gives many similar sequences.
Sequence in context: A069506 A239900 A123165 * A225955 A236073 A064772
Adjacent sequences: A098435 A098436 A098437 * A098439 A098440 A098441


KEYWORD

nonn,more


AUTHOR

Tim Honeywill, Jon Ingram, and Paul Boddington, Oct 26 2004


EXTENSIONS

a(5)a(7), corresponding to probable primes, from Ryan Propper, Jun 25 2005
a(7) = 8447 was found by Richard Fischer in 2004.  Alexander Adamchuk, Feb 11 2007
Edited by N. J. A. Sloane Jan 25 2008 at the suggestion of Herman Jamke (hermanjamke(AT)fastmail.fm)
Edited by T. D. Noe, Oct 30 2008
a(8)a(10) from Robert Price, Dec 10 2011


STATUS

approved



