This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A179625 #32 Apr 03 2023 10:36:12 %S A179625 5,7,13,31,43,73,157,211,241,1093,2801,19531,22621,30941,55987,88741, %T A179625 245411,292561,346201,797161,5229043,8108731,12207031,25646167, %U A179625 305175781,321272407,917087137,16148168401,2141993519227,10778947368421,17513875027111,610851724137931,50544702849929377 %N A179625 Legal generalized repunit prime numbers. %C A179625 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. %H A179625 Charles R Greathouse IV, <a href="/A179625/b179625.txt">Table of n, a(n) for n = 1..640</a>, replacing an earlier file of T. D. Noe %H A179625 Chris Caldwell, <a href="https://t5k.org/top20/page.php?id=16">The Top Twenty: Generalized Repunit</a> %H A179625 Robert Granger and Andrew Moss, <a href="https://arxiv.org/abs/1108.3054">Generalised Mersenne numbers revisited</a>, arXiv:1108.3054 [math.NT], 2011-2012. %t A179625 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]]] %o A179625 (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 %Y A179625 Cf. A076481, A086122, A165210, A102170 (repunit primes in bases 3, 5, 6, and 7) %Y A179625 This sequence except for the term 5 is subsequence of A085104. %K A179625 nonn %O A179625 1,1 %A A179625 _Tim Johannes Ohrtmann_, Jan 09 2011