Search: id:A111934
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%I A111934
%S A111934 1,2,1,2,5,5,5,1,1,5,55,55,55,55,275,275,4675,4675,17765,88825,88825,977075,
%T A111934 22472725,4494545,112363625,112363625,22472725,22472725,130341805,651709025,
%U A111934 651709025,651709025,7168799275,121869587675,609347938375,609347938375
%N A111934 Denominator of f(n) := Product_{i=1..n} sigma(i)/i.
%C A111934 R. K. Guy observes (Nov 23, 2005) that it appears that f(n) is an integer 
               iff n = 1, 3, 8, 9, when f(n) = 1, 2, 18, 26 respectively.
%e A111934 1, 3/2, 2, 7/2, 21/5, 42/5, 48/5, 18, 26, 234/5, 2808/55, 6552/55, 7056/
               55, 12096/55, 96768/275, 187488/275, 3374784/4675, 7312032/4675, 
               29248128/17765, 307105344/88825, ...
%p A111934 with(numtheory); f:=n->mul(sigma(i)/i,i=1..n);
%t A111934 f[n_] := Denominator@ Product[ DivisorSigma[1, i]/i, {i, n}]; Array[f, 
               36] (from Robert G. Wilson v (rgwv(at)rgwv.com), May 01 2006)
%Y A111934 Cf. A111928.
%Y A111934 Sequence in context: A167482 A137327 A143913 this_sequence A098509 A019910 
               A084309
%Y A111934 Adjacent sequences: A111931 A111932 A111933 this_sequence A111935 A111936 
               A111937
%K A111934 nonn,frac
%O A111934 1,2
%A A111934 N. J. A. Sloane (njas(AT)research.att.com), Nov 27 2005

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