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 A058764 #43 Aug 13 2022 17:59:14
%S A058764 2,4,6,12,24,48,96,192,384,768,1536,3072,6144,12288,24576,49152,98304,
%T A058764 196608,393216,786432,1572864,3145728,6291456,12582912,25165824,
%U A058764 50331648,100663296,201326592,402653184,805306368,1610612736,3221225472
%N A058764 Smallest number x such that cototient(x) = 2^n.
%C A058764 Since the cototient of 3*2^n is 2^(n+1), upper bounds are given by A007283(n-1). - _R. J. Mathar_, Oct 13 2008
%C A058764 A058764(n+1) is the number of different walks with n steps in the graph G = ({1,2,3,4}, {{1,2}, {2,3}, {3,4}}). - _Aldo González Lorenzo_, Feb 27 2012
%H A058764 Jud McCranie, <a href="/A058764/b058764.txt">Table of n, a(n) for n = 0..46</a>
%F A058764 a(n) = min { x | A051953(x) = 2^n }.
%F A058764 a(n) = (if n>1 then 3 else 4)*2^(n-1) = A007283(n-1) for n>1. (Conjectured.) - _M. F. Hasler_, Nov 10 2016
%e A058764 a(5) = 48, cototient(48) = 48-Phi(48) = 48-16 = 32. For n>2, a(n) = 3*2^(n-1); largest solutions = 2^(n+1). Prime factors of solutions: 2 and Mersenne-primes were found only.
%t A058764 Function[s, Flatten@ Map[First@ Position[s, #] &, 2^Range[0, Floor@ Log2@ Max@ s]]]@ Table[n - EulerPhi@ n, {n, 10^7}] (* _Michael De Vlieger_, Dec 17 2016 *)
%o A058764 (PARI) a(n) = {x = 1; while(x - eulerphi(x) != 2^n, x++); x;} \\ _Michel Marcus_, Dec 11 2013
%o A058764 (PARI) a(n) = if(n>1,3,4)<<(n-1) \\ _M. F. Hasler_, Nov 10 2016
%Y A058764 Cf. A051953, A053579, A053650.
%Y A058764 Cf. A042950. - _R. J. Mathar_, Jan 30 2009
%Y A058764 Cf. A007283.
%K A058764 nonn,hard
%O A058764 0,1
%A A058764 _Labos Elemer_, Jan 02 2001
%E A058764 Edited by _M. F. Hasler_, Nov 10 2016
%E A058764 a(27)-a(31) from _Jud McCranie_, Jul 13 2017