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%I #39 Oct 29 2014 13:17:01
%S 2,6,16,34,72,122,214,338,516,734,1062,1438,1970,2586,3322,4186,5322,
%T 6566,8152,9898,11896,14114,16838,20254,23982,28196,32746,38108,43710,
%U 50242,57286,64990,73238,82326,91846,102698,114234,126706,139818
%N The sum of denominators of unreduced mediants in Farey sequences of orders 1,2,..,n.
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Mediant_(mathematics)">Mediant</a>.
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Farey_sequence">Farey Sequence</a>.
%F a(n) = 2*Sum_{k= 1,2,3,4..n} A213544(k).
%e For n=4, the unreduced mediants are 1/2, 2/4, 5/10, 9/18, hence the sum of denominators is 2+4+10+18 = 34.
%Y Cf. A007306, A006843.
%K nonn,easy
%O 0,1
%A _Nehul Yadav_, Oct 15 2014
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