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a(n)=Card( k, 0<k<n such that phi(k) divides phi(n-k)).
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%I #5 Mar 30 2012 18:38:58

%S 0,1,2,2,2,3,4,4,5,6,5,5,7,6,7,8,7,9,5,10,9,10,9,7,11,9,10,10,8,9,10,

%T 11,13,12,12,13,11,11,12,14,12,13,8,16,15,16,15,11,19,16,12,15,11,16,

%U 15,17,16,15,10,14,15,12,20,15,20,18,11,17,16,18,16,18,15,18,18,16,18

%N a(n)=Card( k, 0<k<n such that phi(k) divides phi(n-k)).

%o (PARI) for(n=1,100,print1(sum(i=1,n-1,if(eulerphi(n-i)%eulerphi(i),0,1)),","))

%K easy,nonn

%O 1,3

%A _Benoit Cloitre_, May 02 2002