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 A260197 #5 Jul 19 2015 09:01:25
%S A260197 5,277,29,17,43,103,53,31,1571,3089,37,593,881,3023,277,9257,47,1949,
%T A260197 9137,311,17011,1039,53,59,2153,15331,3617,631,44867,61,17351,661,821,
%U A260197 2339,683,1201,34759,62687,20327,59369,71,883,40189,9187,1879,7669,2767,3931,8867,8081,79,12401,139,4787,6367,277,2903,23671,32839,3659
%N A260197 Least prime p such that pi(p*n) = prime(q*n) for some prime q, where pi(x) denotes the number of primes not exceeding x.
%C A260197 Conjecture: a(n) exists for any n > 0. Also, for any n > 0, there are primes p and q such that pi(p*n) = q*n.
%D A260197 Zhi-Wei Sun, Problems on combinatorial properties of primes, in: M. Kaneko, S. Kanemitsu and J. Liu (eds.), Number Theory: Plowing and Starring through High Wave Forms, Proc. 7th China-Japan Seminar (Fukuoka, Oct. 28 - Nov. 1, 2013), Ser. Number Theory Appl., Vol. 11, World Sci., Singapore, 2015, pp. 169-187.
%H A260197 Zhi-Wei Sun, <a href="/A260197/b260197.txt">Table of n, a(n) for n = 1..300</a>
%H A260197 Zhi-Wei Sun, <a href="http://arxiv.org/abs/1402.6641">Problems on combinatorial properties of primes</a>, arXiv:1402.6641 [math.NT], 2014.
%e A260197 a(1) = 5 since pi(5*1) = 3 = prime(2*1) with 2 and 5 both prime.
%e A260197 a(2) = 277 since pi(277*2) = 101 = prime(13*2) with 13 and 277 both prime.
%e A260197 a(10) = 3089 since pi(3089*10) = 3331 = prime(47*10) with 47 and 3089 both prime.
%t A260197 PQ[n_,p_]:=PrimeQ[p]&&PrimeQ[PrimePi[p]/n]
%t A260197 Do[k=0;Label[aa];k=k+1;If[PQ[n,PrimePi[Prime[k]*n]],Goto[bb],Goto[aa]];Label[bb];Print[n, " ", Prime[k]];Continue,{n,1,60}]
%Y A260197 Cf. A000040, A000720, A237578.
%K A260197 nonn
%O A260197 1,1
%A A260197 _Zhi-Wei Sun_, Jul 19 2015