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%I #15 Sep 08 2022 08:46:00
%S 1,1,2,1,1,2,2,1,2,2,1,2,1,1,3,1,1,2,2,1,3,2,1,2,2,1,2,1,1,3,2,1,2,2,
%T 1,2,2,1,2,2,1,3,1,1,3,1,1,2,2,1,3,2,0,2,2,1,3,1,1,3,1,1,2,1,1,3,1,1,
%U 3,2,1,2,1,1,3,2,1,2,2,1,2,2,0,3,2,1,3,1,1,3,2,1,2,1,1,2,2,1,3,2,1,2,1,1,3,2,1,2,1,1,2,2,1,3,2,1,3,1,1,3,2
%N a(n) = floor(phi(2*n+1)/phi(2*n+2)).
%D Dimitris Vathis, Letter to _N. J. A. Sloane_, Apr 22 1985.
%H Harvey P. Dale, <a href="/A199596/b199596.txt">Table of n, a(n) for n = 0..1000</a>
%t Floor[#[[1]]/#[[2]]]&/@Partition[EulerPhi[Range[250]],2] (* _Harvey P. Dale_, May 23 2019 *)
%o (Magma) [EulerPhi(2*n+1) div EulerPhi(2*n+2): n in [0..100]]; // _Vincenzo Librandi_, May 24 2019
%Y Cf. A000010.
%K nonn
%O 0,3
%A _N. J. A. Sloane_, Nov 08 2011