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A197504 A196445(n)/2. 1

%I

%S 1,3,7,9,11,19,23,27,31,43,47,49,59,67,71,79,81,83,103,107,121,127,

%T 131,139,151,163,167,179,191,199,211,223,227,239,243,251,263,271,283,

%U 307,311,331,343,347,359,361,367,379,383,419,431,439,443,463,467,479,487,491,499,503,523,529

%N A196445(n)/2.

%t a[n_] := If[n == 2, 1, EulerPhi[n]/{1, 1, 2, 1}[[Mod[n, 4] + 1]]]; aa = {}; Do[If[OddQ[a[n]], AppendTo[aa, n/2]], {n, 2, 1000}]; aa

%Y Cf. A055035, A196445.

%K nonn

%O 1,2

%A _Artur Jasinski_, Oct 15 2011

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Last modified July 17 23:21 EDT 2019. Contains 325109 sequences. (Running on oeis4.)