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 A161500 #2 Mar 30 2012 17:35:23 %S A161500 2,5,29,41,89,101,109,269,421,509,521,709,929,941,1549,1861,2281,2521, %T A161500 2749,2801,2909,3121,3169,3469,5821,5881,7109,8069,8969,9041,9181, %U A161500 10061,10601,11549,15121,16061,16889,16981,21929,30089,30169,32561,41149 %N A161500 Primes dividing some member of A073833. %C A161500 Primes that divide A073833(n) will divide A073834(m) for any m > n, and this is all the prime divisors of A073834(m). %C A161500 Iterating f(x) = x + 1/x modulo p will eventually either produce a zero (in which case p is in this sequence), or it will loop to an earlier term (in which case it is not). Since f(-x) = -f(x), encountering the negation of an earlier term means that the iteration is looping. %C A161500 Note that A073833(6) = 969581 = 521 * 1861 is the first composite member of that sequence. %o A161500 (PARI) ina(p)=local(m,k,v);m=Mod(1,p);v=vector(p\2);while(m!=0,k=lift(m);if(2*k>p,k=p-k);if(v[k],return(0));v[k]=1;m+=1/m);1 %Y A161500 Cf. A073833, A073834, A000057. %K A161500 nonn %O A161500 1,1 %A A161500 _Franklin T. Adams-Watters_, Jun 11 2009