Search: id:A049108
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%I A049108
%S A049108 1,2,3,3,4,3,4,4,4,4,5,4,5,4,5,5,6,4,5,5,5,5,6,5,6,5,5,5,6,5,6,6,6,6,6,
%T A049108 5,6,5,6,6,7,5,6,6,6,6,7,6,6,6,7,6,7,5,7,6,6,6,7,6,7,6,6,7,7,6,7,7,7,6,
%U A049108 7,6,7,6,7,6,7,6,7,7,6,7,8,6,8,6,7,7,8,6,7,7,7,7,7,7,8,6,7,7,8,7,8,7,7
%N A049108 Number of iterations of Euler phi function needed to reach 1 starting 
               at n (n is counted).
%F A049108 By the definition of a(n) we have for n >= 2 the recursion a(n) = a(Phi(n)) 
               + 1. - Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 20 2001
%e A049108 If n=164 the trajectory is {164,80,32,16,8,4,2,1}. Its length is 8, thus 
               a(164)=8.
%t A049108 f[n_] := Length[ NestWhileList[ EulerPhi, n, Unequal, 2]] - 1; Table[ 
               f[n], {n, 1, 105}]
%Y A049108 Cf. A000010, A007755. Equals A003434 + 1.
%Y A049108 Sequence in context: A096344 A030349 A085887 this_sequence A086925 A088858 
               A113312
%Y A049108 Adjacent sequences: A049105 A049106 A049107 this_sequence A049109 A049110 
               A049111
%K A049108 nonn,nice,easy
%O A049108 1,2
%A A049108 Labos E. (labos(AT)ana.sote.hu)

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