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 A072076 #26 Feb 09 2022 18:42:23
%S A072076 2,22,250,3750,41250,414150,4166250,42281250,438281250,4400343750,
%T A072076 44266406250,449238281250,4510352343750,45373066406250,
%U A072076 455545586718750,4555455867187500,45555287544813750,455552875448137500,4566844506855468750,45668445068554687500
%N A072076 Largest k such that EulerPhi(k) = 10^n.
%H A072076 Ray Chandler, <a href="/A072076/b072076.txt">Table of n, a(n) for n = 0..1000</a>
%H A072076 Max A. Alekseyev, <a href="https://www.emis.de/journals/JIS/VOL19/Alekseyev/alek5.html">Computing the Inverses, their Power Sums, and Extrema for Euler's Totient and Other Multiplicative Functions</a>. Journal of Integer Sequences, Vol. 19 (2016), Article 16.5.2
%F A072076 a(n) = Max{k; A000010(k) = 10^n}.
%e A072076 n=3: a(3)=3750 because InvPhi(1000) = {1111, 1255, 1375, 1875, 2008, 2222, 2500, 2510, 2750, 3012, 3750}.
%Y A072076 Cf. A000010, A014197, A014573, A072074, A072075, A110076.
%K A072076 nonn
%O A072076 0,1
%A A072076 _Labos Elemer_, Jun 13 2002
%E A072076 More terms from _Max Alekseyev_, Apr 26 2010