Search: id:A113479
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%I A113479
%S A113479 4,8,32,128,256,512,4096,32768,65536,131072,524288,2097152,4194304,
%T A113479 8388608,134217728,2147483648,4294967296,8589934592,34359738368,
%U A113479 137438953472,274877906944,549755813888,4398046511104,35184372088832
%N A113479 Starting with the fraction 4/1 as the first term, a(n) is the numerator 
               of the reduced fraction of the n-th term according to the rule: if 
               n is even, multiply the previous term by n/(n+1) otherwise multiply 
               the previous term by (n+1)/n.
%C A113479 The fractions forming these numerators slowly converge to Pi. The 1000th 
               term at 2000 digits precision yields 3.1400...
%D A113479 John Derbshire, Prime Obsession, 2004, Joseph Henry Press, p. 16.
%e A113479 The first term is 4/1. then the 2nd term is 4/1*2/(2+1) = 8/3. So 8 is 
               the 2nd entry in the table.
%o A113479 (PARI) g(n) = { a=4;b=1; print1(4","); for(x=2,n, if(x%2==0,a=a*x;b=b*(x+1),
               a=a*(x+1);b=b*x); print1(numerator(a/b)",") ) }
%Y A113479 Sequence in context: A149094 A086344 A068205 this_sequence A103970 A034785 
               A075398
%Y A113479 Adjacent sequences: A113476 A113477 A113478 this_sequence A113480 A113481 
               A113482
%K A113479 easy,frac,nonn
%O A113479 1,1
%A A113479 Cino Hilliard (hillcino368(AT)gmail.com), Jan 09 2006

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