OFFSET
1,1
COMMENTS
In Chris Caldwell's sense, a legal generalized repunit prime is a prime number of the form (b^p-1)/(b-1) such that 3 <= b <= 5*p, b != 10, and p prime.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..640, replacing an earlier file of T. D. Noe
Chris Caldwell, The Top Twenty: Generalized Repunit
Robert Granger and Andrew Moss, Generalised Mersenne numbers revisited, arXiv:1108.3054 [math.NT], 2011-2012.
MATHEMATICA
lim=10^17; n=1; Sort[Reap[While[p=Prime[n]; b=3; While[num=Cyclotomic[p, b]; b<=5p && num<=lim, If[b!=10 && PrimeQ[num], Sow[num]]; b++]; b>3, n++]][[2, 1]]]
PROG
(PARI) upTo(lim)=my(v=List(), t); forprime(p=2, log(2*lim+1)\log(3), for(b=3, 5*p, if(b==10, next); t=(b^p-1)/(b-1); if(t>lim, break); if(isprime(t), listput(v, t)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Aug 21 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Tim Johannes Ohrtmann, Jan 09 2011
STATUS
approved