Search: id:A071575
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%I A071575
%S A071575 0,1,1,2,1,3,1,3,2,4,1,4,1,4,2,4,1,5,1,5,3,5,1,5,2,5,3,5,1,6,1,5,2,6,2,
               6,
%T A071575 1,6,3,6,1,7,1,6,4,6,1,6,2,7,2,6,1,7,3,6,4,7,1,7,1,6,4,6,2,7,1,7,3,7,1,
%U A071575 7,1,7,3,7,2,8,1,7,4,8,1,8,4,7,2,7,1,8,2,7,3,7,2,7,1,7,4,8,1,8,1,7,5,8
%N A071575 Number of iterations of cototient(n) needed to reach 1 (cototient(x) 
               = x-phi(x)).
%C A071575 Equals A076640(n)-1.
%H A071575 T. D. Noe, <a href="b071575.txt">Table of n, a(n) for n=1..10000</a>
%F A071575 a(n) = a(n-phi(n))+1, a(1) = 0.
%e A071575 cototient(6) = 4 cototient(4) = 2 cototient(2) = 1 hence a(6) = 3
%o A071575 (PARI) for(n=1,150,s=n; t=0; while(s!=1,t++; s=s-eulerphi(s); if(s==1,
               print1(t,","); ); ))
%Y A071575 Cf. A032358.
%Y A071575 Sequence in context: A029231 A025808 A144079 this_sequence A038569 A020650 
               A124224
%Y A071575 Adjacent sequences: A071572 A071573 A071574 this_sequence A071576 A071577 
               A071578
%K A071575 easy,nonn
%O A071575 1,4
%A A071575 Benoit Cloitre (benoit7848c(AT)orange.fr), May 31 2002
%E A071575 Prepended a(1)=0 and changed offset. - T. D. Noe (noe(AT)sspectra.com), 
               Dec 03 2008

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