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 A083750 #7 Mar 31 2012 14:40:08 %S A083750 85,145,304,915 %N A083750 Numbers n such that 2111131111...p(n-1)1111p(n) is prime. %C A083750 Let fp(n,k) be the decimal concatenation of prime(n), k, and fp(n-1,k) for n > 1, and fp(1,k) = 2. Then a(n) = fp(n, 1111). %C A083750 No more terms up to 6300. %H A083750 Farideh Firoozbakht, <a href="http://www.primepuzzles.net/puzzles/puzz_208.htm">On Solution of puzzle 208 </a>. %e A083750 a(1)=85 because fp(85,1111)= 211113111151111...4331111439 is prime and fp(k,1111) is composite for k< 85 (prime(85)=439). %e A083750 a(3)=304 because fp(304,1111)=211113111151111...199911112003 is a prime related to prime year 2003; this prime number has 2231 digits. fp(915,1111)=211113111151111...712911117151 is a prime with 7119 digits (prime(915)=7151). %Y A083750 Cf. A083677, A082549. %K A083750 nonn,base %O A083750 1,1 %A A083750 _Farideh Firoozbakht_, Jun 17 2003 %E A083750 Comment from _Charles R Greathouse IV_, Oct 12 2009