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 A070639 #16 Aug 10 2020 22:14:42
%S A070639 1,3,5,9,11,20,19,31,33,48,43,73,59,90,88,111,97,159,121,182,165,208,
%T A070639 173,277,211,290,263,338,271,445,309,435,396,490,414,608,433,610,544,
%U A070639 695,531,844,585,818,745,880,697,1080,773,1085,918,1126,883,1364,995
%N A070639 a(n) = (1/phi(n))*Sum_{k=1..n} phi(n*k).
%C A070639 a(2n)>a(2n+1) for n>=5.
%C A070639 If n is prime, a(n) = A002088(n)+1. - _Robert Israel_, Aug 10 2020
%H A070639 Robert Israel, <a href="/A070639/b070639.txt">Table of n, a(n) for n = 1..2000</a>
%p A070639 f:= n -> add(numtheory:-phi(n*k),k=1..n)/numtheory:-phi(n);
%p A070639 map(f, [$1..100]); # _Robert Israel_, Aug 10 2020
%t A070639 Table[1/EulerPhi[n]*Sum[EulerPhi[n*k],{k,n}],{n,60}] (* _Harvey P. Dale_, Dec 21 2015 *)
%o A070639 (PARI) for(n=1,100,print1(sum(i=1,n,eulerphi(n*i))/eulerphi(n),","))
%Y A070639 Cf. A002088.
%K A070639 easy,nonn,look
%O A070639 1,2
%A A070639 _Benoit Cloitre_, May 13 2002