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%I A245678 #4 Jul 30 2014 16:58:45
%S A245678 2,3,12,5,60,35,280,63,2520,77,27720,1287,8008,6435,144144,2431,
%T A245678 2450448,46189,3695120,146965,232792560,96577,1070845776,1300075,
%U A245678 2974571600,5014575,11473347600,215441,332727080400,31556720475,486207248800,20419054425
%N A245678 Denominator of sum of fractions A182972(k) / A182973(k) such that A182972(k) + A182973(k) = n.
%C A245678 A182972(n) and A182973(n) provide an enumeration of positive rationals < 1 arranged by increasing sum of numerator and denominator then by increasing numerator;
%C A245678 a(n) = denominator(sum(A182972(k)/A182973(k): k such that A182972(k)+A182973(k)=n));
%C A245678 A245718(n) = floor(A245677(n)/a(n)).
%H A245678 Reinhard Zumkeller, <a href="/A245678/b245678.txt">Table of n, a(n) for n = 3..1000</a>
%H A245678 Paul Yiu, <a href="http://math.fau.edu/Yiu/RecreationalMathematics2003.pdf">Recreational Mathematics</a>, 24.3.1 Appendix: Two enumerations of the rational numbers in (0,1), page 633.
%e A245678 See A245677.
%o A245678 (Haskell)
%o A245678 import Data.Ratio ((%), denominator)
%o A245678 a245678 n = denominator $ sum
%o A245678    [num % den | num <- [1 .. div n 2], let den = n - num, gcd num den == 1]
%Y A245678 Cf. A245677 (numerator), A182972, A182973, A245718.
%K A245678 nonn,frac
%O A245678 3,1
%A A245678 _Reinhard Zumkeller_, Jul 30 2014

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