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 A073455 #8 Apr 06 2018 17:40:10
%S A073455 6,12,18,24,42,60
%N A073455 Numbers n such that to phi(n) = pi(n)-1.
%e A073455 9 primes below 24 = {2,3,5,7,11,13,17,19,23}; RRS[24]={1,5,7,11,13,17,19,23}, so 24 is here.
%t A073455 Do[s=EulerPhi[n]-PrimePi[n]; If[Equal[s, -1], Print[n]], {n, 1, 10000}]
%Y A073455 Cf. A037228, A037171, A000010, A000720.
%K A073455 fini,full,nonn
%O A073455 1,1
%A A073455 _Labos Elemer_, Aug 02 2002