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 A048867 #14 May 14 2017 03:15:43 %S A048867 1,2,11,13,17,19,23,25,27,29,31,33,35,37,39,41,43,47,49,51,53,55,57, %T A048867 59,61,63,65,67,69,71,73,75,77,79,81,83,85,87,89,91,93,94,95,97,99, %U A048867 101,103,106,107,109,111,113,115,117,118,119,121,122,123,124,125,127,128 %N A048867 Numbers for which reduced residue system contains fewer primes than nonprimes. %C A048867 Integers n such that 2*A000720(n) - 2*A001221(n) < A000010(n). %H A048867 G. C. Greubel, <a href="/A048867/b048867.txt">Table of n, a(n) for n = 1..1000</a> %e A048867 Large primes belong to this set. Composites like: n=35 has 2 prime divisors, Phi(35)=24 Pi(35)=11; In reduced residue system 9 primes and 15 nonprimes occur. %t A048867 Select[Range[500], 2*PrimePi[#] - 2*PrimeNu[#] < EulerPhi[#] &] (* _G. C. Greubel_, May 12 2017 *) %o A048867 (PARI) isok(n) = 2*(primepi(n) - omega(n)) < eulerphi(n); \\ _Michel Marcus_, May 13 2017 %Y A048867 Cf. A000010, A000720, A001221. %K A048867 nonn %O A048867 1,2 %A A048867 _Labos Elemer_