cp's OEIS Frontend

A104527 Denominator of sum(1/(phi(k)sigma(k)),k=1..n), where phi(k) is the totient function and sigma(k) is the sum of the divisors function.

%I A104527 #2 Mar 30 2012 17:36:01
%S A104527 1,3,24,168,7,168,112,1680,21840,65520,65520,16380,32760,21840,29120,
%T A104527 902720,8124480,8124480,1624896,1624896,3249792,5416320,59579520,
%U A104527 59579520,59579520,178738560,178738560,178738560,178738560,178738560
%N A104527 Denominator of sum(1/(phi(k)sigma(k)),k=1..n), where phi(k) is the totient function and sigma(k) is the sum of the divisors function.
%C A104527 The first 5 sums are: 1,4/3,35/24,257/168,11/7.
%e A104527 a(3)=24 because phi(1)*sigma(1)+phi(2)*sigma(2)+phi(3)*sigma(3)=1/(1*1)+1/(1*3)+1/(2*4)=35/24.
%p A104527 with(numtheory): a:=n->denom(sum(1/phi(k)/sigma(k),k=1..n)): seq(a(n),n=1..35);
%Y A104527 Cf. A104526, A093827.
%K A104527 frac,nonn
%O A104527 1,2
%A A104527 _Emeric Deutsch_, Mar 12 2005