This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A121709 #2 Mar 31 2012 13:20:28
%S A121709 1,4,2,5,13,1,73,5,7,1,37,5,1361,1,223,25,4673,1,24473,25,16019,1,
%T A121709 83879,65,62743,1,20533,65,1505173,1,7881193,85,5158309,1,27009259,
%U A121709 425,1400221,1,1446283,2225,69237359,1,51790217,445,1660959719,1,8696897999
%N A121709 Numerator of Sum/Product of first n Lucas numbers A000032[n].
%C A121709 5 divides a(4k). a(1) = 1 and a(4k+2) = 1 for k>0.
%F A121709 a(n) = Numerator[Sum[Lucas[k],{k,1,n}]/Product[Lucas[k],{k,1,n}]], where Lucas[k] = Fibonacci[k-1] + Fibonacci[k+1].
%t A121709 Table[Numerator[Sum[Fibonacci[k-1]+Fibonacci[k+1],{k,1,n}]/Product[Fibonacci[k-1]+Fibonacci[k+1],{k,1,n}]],{n,1,100}]
%Y A121709 Cf. A000045, A000032, A079451, A001578, A096362, A058036, A121708, A090585.
%K A121709 frac,nonn
%O A121709 1,2
%A A121709 _Alexander Adamchuk_, Aug 16 2006