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 A075601 #5 Dec 05 2013 19:55:39 %S A075601 13,2131,121313,51213137,3512131379,135121313797,21351213137977, %T A075601 5213512131379777,352135121313797771,63521351213137977713, %U A075601 16352135121313797771319,9163521351213137977713193 %N A075601 a(1) = 13 and then the smallest prime that is obtained by placing digits on both sides of the previous term. Or smallest prime that encompasses a(n-1). %Y A075601 Cf. A075595, A075596, A075597, A075598, A075599, A075600, A075602. %K A075601 base,nonn %O A075601 1,1 %A A075601 _Amarnath Murthy_, Sep 28 2002 %E A075601 Corrected and extended by _Sascha Kurz_, Jan 23 2003