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 A110704 #6 Mar 30 2012 17:29:49
%S A110704 43,4243,424243,42424243,4242424243,4242424242424243,
%T A110704 424242424242424242424242424242424243,
%U A110704 42424242424242424242424242424242424242424242424243
%N A110704 Primes of form "n 42's followed by 43".
%C A110704 Products of first three (77402711107), four (3283751424862167001) and five (13931066652821050218557005243) terms are Zeisel numbers (A051015) with coefficients (100,-57).
%t A110704 t = 1; Do[ t = t*100 - 57; If[PrimeQ[t], Print[t]], {n, 0, 24}]
%Y A110704 Cf. A110705.
%K A110704 nonn
%O A110704 1,1
%A A110704 _Ray Chandler_, Aug 04 2005