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 A098217 #11 Jul 11 2019 02:08:29
%S A098217 0,2,4,4,3,6,8,8,7,8,9,5,9,22,11,7,44,44,66,33,88,11,33,55,88,55,99,
%T A098217 111,77,33,99,99,111,77,77,111,55,333,55,77,444,99,333,333,77,111,77,
%U A098217 99,77,77,777,888,888,111,99,999,777,111,99,99,555,111,999,999,999,111,1111
%N A098217 Cototients of terms from A098216. By definitions these cototient values are decimal repdigits.
%C A098217 It is believed that for every repdigit r>1, inverse[cototient[r]] has solution, usually more than one.
%t A098217 ta={{0}};Do[s=Length[Union[IntegerDigits[n-EulerPhi[n]]]]; If[Equal[s, 1]&&!PrimeQ[n], Print[{n, n-EulerPhi[n]}];ta=Append[ta, n]], {n, 1, 100000}];ta=Delete[ta, 1];ta-EulerPhi[ta]
%Y A098217 Cf. A096503, A010785, A098216.
%K A098217 nonn,base
%O A098217 1,2
%A A098217 _Labos Elemer_, Oct 22 2004