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 A179891 Composites h such that antiharmonic mean B(h) of the numbers k < h such that GCD(k, h) = 1 is not integer. 22

%I

%S 4,6,8,9,12,14,15,16,18,20,21,24,25,26,27,28,30,32,33,35,36,38,39,40,

%T 42,44,45,48,49,50,51,52,54,56,57,60,62,63,64,65,66,68,69,70,72,74,75,

%U 76,77,78,80,81,84,86,87,88,90,92,93,95,96,98,99,100,102,104,105,108,111

%N Composites h such that antiharmonic mean B(h) of the numbers k < h such that GCD(k, h) = 1 is not integer.

%C Composites h such that B(h) = A053818(h) / A023896(h) = A175505(h) / A175506(h) is not integer. Composites h such that A175506(h) > 1. Subsequence of A179872. Union a(n) + A007645 = A179872.

%H G. C. Greubel, <a href="/A179891/b179891.txt">Table of n, a(n) for n = 1..1749</a>

%e a(6) = 14 because B(14) = A053818(14) / A023896(14) = 406 / 42 = 29 / 3 (not integer).

%t f[n_] := 2 Plus @@ (Select[ Range@n, GCD[ #, n] == 1 &]^2)/(n*EulerPhi@n); Select[ Range@ 111, ! PrimeQ@# && ! IntegerQ@f@# &] (* _Robert G. Wilson v_, Aug 02 2010 *)

%Y Cf. A179871, A179872, A179873, A179874, A179875, A179876, A179877, A179878, A179879, A179880, A179882, A179883, A179884, A179885, A179886, A179887, A179890.

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Jul 30 2010

%E More terms from _Robert G. Wilson v_, Aug 02 2010

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Last modified March 24 19:48 EDT 2019. Contains 321448 sequences. (Running on oeis4.)