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%I #17 Apr 26 2021 21:23:34
%S 2,3,5,6,7,9,10,11,12,16,17,20,21,22,23,24,61,62,63,673,674,675,725,
%T 726,727,728,733,734,735,736,737,738,739,740,741,742,743,744,745,784,
%U 785,786,787,788,789,790,791,792,793,797,798,799,800,801,802,803,804
%N Numbers k such that Sum_{i=1..k} mu(sigma(i)) = 0.
%H Harry J. Smith, <a href="/A065000/b065000.txt">Table of n, a(n) for n = 1..1000</a>
%t Position[Accumulate[MoebiusMu[DivisorSigma[1,Range[1000]]]],0]//Flatten (* _Harvey P. Dale_, Aug 15 2016 *)
%o (PARI) { n=s=0; for (m=1, 10^9, s+=moebius(sigma(m)); if (s==0, write("b065000.txt", n++, " ", m); if (n==1000, return)) ) } \\ _Harry J. Smith_, Oct 03 2009
%K nonn
%O 1,1
%A _Benoit Cloitre_, Feb 19 2002