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 A053147 #25 Jul 12 2021 11:13:56
%S A053147 2,4,8,32,32,256,32,512,256,65536,64,512,4096,256,512,128,16,2048,64,
%T A053147 64,512,8192,256,8192,2048,131072,128,8192,1048576,16,2048,2048,32768,
%U A053147 8192,512,524288,8192,64,16,8192,16,16,256,16
%N A053147 When cototient function (A051953) is iterated with initial value A002110(n), a(n) is the value of first (largest) power of 2 which appears in the iteration.
%C A053147 In these iteration chains the number of non-2-powers seem to be dominant.
%C A053147 The sequence is not monotonic.
%e A053147 For n=10, the iteration chain of 43 terms is {6469693230, 5447823150, 4315810350, ..., 188416, 98304, 65536, 32768, ..., 4, 2, 1, 0} in which the largest power of 2 is 65536 = 2^16.
%e A053147 For n=11 the length is 61, including 54 numbers that are not powers of 2, and 7 powers of 2, of which the largest is 64 = a(11) < a(10) = 65536.
%t A053147 Table[SelectFirst[NestWhileList[# - EulerPhi@ # &, P, # > 0 &], IntegerQ@ Log2@ # &], {P, FoldList[Times, Prime@ Range@ 30]}] (* _Michael De Vlieger_, Jun 11 2018 *)
%Y A053147 Cf. A002110, A051953.
%K A053147 nonn,more
%O A053147 1,1
%A A053147 _Labos Elemer_, Feb 28 2000
%E A053147 More terms from _Michael De Vlieger_, Jun 11 2018
%E A053147 a(41)-a(44) from _Jinyuan Wang_, Jul 12 2021