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%I #16 Jan 03 2017 02:29:20
%S 2,2,4,6,4,4,6,8,8,6,8,12,10,8,20,12,18,12,8,16,20,16,24,12,18,24,16,
%T 12,20,24,22,16,42,20,32,24,18,40,24,36,28,16,30,36,32,48,20,32,44,24,
%U 24,36,40,36,60,24,32,54,40,24,64,42,56,40,24,72,44,60,46,72,32,42,60
%N a(n) = phi(n-th composite number).
%H Vincenzo Librandi, <a href="/A073256/b073256.txt">Table of n, a(n) for n = 1..1200</a>
%F a(n) = A000010(A002808(n)).
%e 100th composite is 133; phi(133) = 108 = a(100).
%t c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Table[EulerPhi[c[w], {w, 1, 128}]
%t With[{nn=100},EulerPhi[#]&/@Complement[Range[2,nn], Prime[Range[ PrimePi[ nn]]]]] (* _Harvey P. Dale_, Apr 28 2014 *)
%Y Cf. A000010, A002808, A035004, A073255.
%K nonn
%O 1,1
%A _Labos Elemer_, Jul 22 2002
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