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 A064016 #29 Apr 18 2021 06:14:29
%S A064016 0,23,2006,196308,19607514,1960399246,196036947608,19603648572758,
%T A064016 1960364533634092,196036449326991586,19603644912113783634,
%U A064016 1960364490766613788860,196036449073440195974090,19603644907302101080472556,1960364490729905106089642146,196036449072986990521291164848
%N A064016 a(n) = Sum_{k <= 10^n} cototient(k), where cototient is A051953.
%C A064016 It appears that lim_{n->infinity} (1/n^2) * Sum_{j=1..n} a(j) = 0.1960364... = (1/2 - 3/Pi^2).
%F A064016 a(n) = 10^n*(10^n+1)/2 - A002088(10^n) = 10^n*(10^n+1)/2 - A064018(n). - _Chai Wah Wu_, Apr 18 2021
%F A064016 a(n) = A063985(10^n). - _Michel Marcus_, Apr 18 2021
%t A064016 s = 0; k = 1; Do[ While[ k <= 10^n, s = s + k - EulerPhi[ k ]; k++ ]; Print[ s ], {n, 0, 8} ]
%Y A064016 Cf. A002088, A051953, A063985, A064018.
%K A064016 nonn
%O A064016 0,2
%A A064016 _Robert G. Wilson v_, Sep 07 2001
%E A064016 a(9) from _Jud McCranie_, Jun 25 2005
%E A064016 a(10)-a(11) from _Donovan Johnson_, Feb 06 2010
%E A064016 a(12) from _Donovan Johnson_, Feb 07 2012
%E A064016 a(13)-a(15) using A064018 from _Chai Wah Wu_, Apr 18 2021