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 A176797 Antiharmonic means of divisors of antiharmonic numbers. 8

%I

%S 1,3,7,11,13,21,21,43,35,43,61,63,85,111,77,157,91,129,119,147,185,

%T 171,273,183,255,343,231,301,245,255,333,313,507,301,455,481,521,425,

%U 471,547,473,455,813,441,931,629,559

%N Antiharmonic means of divisors of antiharmonic numbers.

%C Values of sigma_2(n) / sigma(n) corresponding to terms of A020487(n), where sigma_2(n) is the sum of squares of divisors of n (A001157) and sigma(n) is the sum of the divisors of n (A000203).

%H Amiram Eldar, <a href="/A176797/b176797.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = (A001157(A020487(n))) / (A000203(A020487(n))).

%e For n = 4; a(4) = 11 because A020487(4) = 16; A001157(16) = 341, A000203(n) = 31, antiharmonic means of divisors of 16 = 341 / 31 = 11.

%t Select[DivisorSigma[2, #]/DivisorSigma[1, #] & /@ Range, IntegerQ] (* _Amiram Eldar_, Sep 18 2019 *)

%K nonn,look

%O 1,2

%A _Jaroslav Krizek_, Apr 26 2010

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Last modified September 26 09:15 EDT 2021. Contains 347664 sequences. (Running on oeis4.)