Search: id:A121594
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%I A121594
%S A121594 15,28,75,77,104,187,196,203,210,222,228,235,238,328,345,375,551,620,
%T A121594 847,888,1036,1107,1204,1349,1352,1372,1391,1430,1457,1469,1470,1498,
%U A121594 1666,1687,1855,1875,2133,2301,2425,2440,2556,2678,2948,3179,3337,3477
%N A121594 Numbers n such that n does not divide the denominator of the n-th alternating 
               Harmonic number.
%C A121594 Indices n such that A119788[n] is not equal to 1.
%C A121594 Also indices n such that numerators of n*H'[n]= A119787[n] and H'[n] 
               = A058313[n] are different ( H'[n] is alternating harmonic number 
               H'[n] = Sum[(-1)^(k+1)*1/k,{k,1,n}] ). The ratio of numerators A119787[n]/
               A058313[n] for n=1..400 is given in A119788[n]. A121595[n] = A119788[a(n)] 
               is compressed version of A119788[n] (all 1 entries are excluded).
%t A121594 Do[H=Sum[(-1)^(i+1)*1/i, {i, 1, n}]; a=Numerator[n*H]; b=Numerator[H]; 
               If[ !Equal[a,b],Print[{n,a/b}]],{n,1,6000}]
%t A121594 f=0;Do[f=f+(-1)^(n+1)/n;If[ !IntegerQ[Denominator[f]/n],Print[n]],{n,
               1,100}] - Alexander Adamchuk (alex(AT)kolmogorov.com), Jan 02 2007
%Y A121594 Cf. A119788, A119787, A058313, A121595.
%Y A121594 Cf. A058312 = Denominator of the n-th alternating harmonic number, sum 
               ((-1)^(k+1)/k, k=1..n). A074791 = numbers n such that n does not 
               divide the denominator of the n-th Harmonic number.
%Y A121594 Sequence in context: A045192 A039285 A043888 this_sequence A163286 A022997 
               A051121
%Y A121594 Adjacent sequences: A121591 A121592 A121593 this_sequence A121595 A121596 
               A121597
%K A121594 nonn
%O A121594 1,1
%A A121594 Alexander Adamchuk (alex(AT)kolmogorov.com), Aug 09 2006

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