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%I #11 Jan 12 2024 01:27:31
%S 1,1,2,2,4,3,5,6,4,6,8,6,11,12,14,8,10,12,12,12,20,20,16,20,16,26,18,
%T 24,18,24,32,22,36,20,24,27,41,42,44,24,36,32,42,30,24,36,56,36,56,48,
%U 32,50,64,65,66,36,44,48,46,72,48,60,48,78,40,48,86,56,80,89,60,60,54,95,96,60
%N a(n) = phi(phi(p))/2 where p = prime(n).
%C Offset is 3 as a(1) and a(2) would be fractional. - _Michel Marcus_, Aug 13 2013
%H Amiram Eldar, <a href="/A094051/b094051.txt">Table of n, a(n) for n = 3..10000</a>
%F From _Amiram Eldar_, Jan 12 2024: (Start)
%F a(n) = A008330(n)/2.
%F a(n) = A023022(A000040(n)-1). (End)
%t EulerPhi[Prime[Range[3, 100]] - 1]/2 (* _Amiram Eldar_, Jan 12 2024 *)
%o (PARI) a(n) = eulerphi(eulerphi(prime(n)))/2; \\ _Michel Marcus_, Aug 13 2013
%Y Cf. A000010, A000040, A008330, A023022.
%K nonn,easy
%O 3,3
%A _Matthijs Coster_, Apr 29 2004
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