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 A117508 #2 Mar 31 2012 13:20:12 %S A117508 3,21,3003,969969,872002131,1537339756953,5532885785273847, %T A117508 28676947025074349001,298326279901848452657403, %U A117508 3479379402495258503343291189,66257821961717207679166294112127 %N A117508 Denominators of partial sums of the Brun series divided by 5. %C A117508 Numerators divided by 4 are given by A117507. %C A117508 See A117507 for more information. %F A117508 a(n)=denominator(r(n))/5, with r(n):=sum(1/ltp(k) + 1/(ltp(k)+2),k=1..n), n>=1, with ltp(k):=A001359(k) (lesser twin primes). %K A117508 nonn,easy,frac %O A117508 1,1 %A A117508 _Wolfdieter Lang_, Apr 13 2006