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Denominator of Sum_{k=1..n} 1/tau(k), where tau(k) is the number of divisors function.
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%I #4 Dec 18 2012 08:39:58

%S 1,2,1,3,6,12,12,6,6,12,12,12,12,6,12,60,60,20,20,60,15,60,60,120,40,

%T 40,40,120,120,30,15,30,60,15,60,180,180,45,180,360,360,45,90,45,90,

%U 180,180,180,180,180,90,45,90,360,360,45,180,90,45,180,180,90,45,315,1260

%N Denominator of Sum_{k=1..n} 1/tau(k), where tau(k) is the number of divisors function.

%H Harvey P. Dale, <a href="/A104529/b104529.txt">Table of n, a(n) for n = 1..1000</a>

%e 1,3/2,2,7/3,17/6

%e a(4)=3 because 1/tau(1)+1/tau(2)+1/tau(3)+1/tau(4)=1/1+1/2+1/2+1/3=7/3.

%p with(numtheory): a:=n->denom(sum(1/tau(k),k=1..n)): seq(a(n),n=1..70);

%t Denominator[Accumulate[1/#&/@DivisorSigma[0,Range[70]]]] (* _Harvey P. Dale_, Dec 18 2012 *)

%Y Cf. A104528.

%K frac,nonn

%O 1,2

%A _Emeric Deutsch_, Mar 12 2005