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