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A070556 a(n) = cototient(totient(n)).

%I A070556 #16 Sep 08 2022 08:45:05
%S A070556 0,0,1,1,2,1,4,2,4,2,6,2,8,4,4,4,8,4,12,4,8,6,12,4,12,8,12,8,16,4,22,
%T A070556 8,12,8,16,8,24,12,16,8,24,8,30,12,16,12,24,8,30,12,16,16,28,12,24,16,
%U A070556 24,16,30,8,44,22,24,16,32,12,46,16,24,16,46,16,48
%N A070556 a(n) = cototient(totient(n)).
%H A070556 G. C. Greubel, <a href="/A070556/b070556.txt">Table of n, a(n) for n = 1..10000</a>
%F A070556 a(n) = A051953(A000010(n)).
%p A070556 A051953 := proc(n)
%p A070556         n-numtheory[phi](n) ;
%p A070556 end proc:
%p A070556 A070556 := proc(n)
%p A070556         A051953(numtheory[phi](n)) ;
%p A070556 end proc: # _R. J. Mathar_, Oct 13 2011
%t A070556 Table[EulerPhi[n] - EulerPhi[EulerPhi[n]], {n, 80}] (* _Vincenzo Librandi_, Aug 06 2015 *)
%o A070556 (Magma) [EulerPhi(n)-EulerPhi(EulerPhi(n)): n in [1..100]]; // _Vincenzo Librandi_, Aug 06 2015
%Y A070556 Cf. A000010, A051953, A054571.
%K A070556 nonn,look
%O A070556 1,5
%A A070556 _N. J. A. Sloane_, May 06 2002