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 A062983 #12 Dec 15 2017 17:35:18
%S A062983 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,
%T A062983 28,29,30,31,32,33,34,35,36,37,38,41,42,43,44,45,46,47,48,49,50,51,52,
%U A062983 53,54,55,56,57,59,60,61,62,63,64,66,67,68,69,70,71,72,73,74,75,76,77
%N A062983 Mertens's function of n (A002321) is not divisible by phi(n).
%t A062983 M[n_]:= Sum[MoebiusMu[k], {k, 1, n}]; Select[Range[250], Mod[M[#], EulerPhi[#]]!=0 &] (* _Indranil Ghosh_, Mar 16 2017 *)
%o A062983 (PARI) M(n)=sum(k=1,n,moebius(k)); j=[]; for(n=1,250, if(Mod(M(n),eulerphi(n))!=0,j=concat(j,n))); j
%Y A062983 Cf. A002321.
%K A062983 nonn
%O A062983 1,1
%A A062983 _Jason Earls_, Jul 25 2001