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 A117631 #7 Nov 21 2013 12:48:57
%S A117631 433640083,1300920277,3902760919,1300920311,3902760991,285567881,
%T A117631 19923341,59770063,432073,432097,259271,777857,2333579,72173,43321,
%U A117631 130043,390151,40361,121171,363541,4211,12647,12653,1151,3467,10427,467
%N A117631 a(1)=433640083; a(n+1)= the largest prime factor of a(n)+b(n)+c(n), where a(n)<b(n)<c(n) and a(n),b(n) and c(n) are three consecutive primes.
%C A117631 Note that before entering the cycle (41, 131, 37, 11) there are 34 terms of the sequence a(1),a(2),...,a(33)=53 and a(34)=173.
%H A117631 Carlos Rivera, <a href="http://www.primepuzzles.net/puzzles/puzz_354.htm">Puzzle 354</a>.
%F A117631 If k is a natural number then a(4k+31)=41; a(4k+32)=131; a(4k+33)=37 and a(4k+34)=11.
%e A117631 a(1)=433640083 so b(1)=nextprime(433640083)=433640093 and c(1)=nextprime(433640093)=433640101 hence a(2) equals largest prime factor of 433640083+433640093+433640101.
%e A117631 But 433640083+433640093+433640101=1300920277 is prime so a(2)= 1300920277.
%t A117631 np[n_]:=Module[{np1=NextPrime[n],np2},np2=NextPrime[np1];Max[Transpose[ FactorInteger[n+np1+np2]]]]; NestList[np,433640083,50] (* _Harvey P. Dale_, Sep 22 2011 *)
%Y A117631 Cf. A109756.
%K A117631 easy,nonn
%O A117631 1,1
%A A117631 Enoch Haga and _Farideh Firoozbakht_, Apr 08 2006