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 A083996 #8 Sep 01 2021 03:40:45 %S A083996 1,3,9,3,11,1,23,49,21,3,17,9,13,3,47,19,41,43,3,51,371,183,3,21,103, %T A083996 53,33,33,91,41,99,433,443,93,111,501,73,11,139,177,171,429,521,333, %U A083996 417,1,341,213,253,171,387,171,779,463,687,861,1131,39,539,231,1513,263,369 %N A083996 a(1) = 1; then numbers such that the concatenation a(n)a(n-1)...a(2)a(1)a(2)...a(n-1)a(n) is a prime for n>1. %Y A083996 Cf. A083997, A083998, A083999, A084000, A083401. %K A083996 base,nonn %O A083996 1,2 %A A083996 _Amarnath Murthy_, May 23 2003 %E A083996 More terms from _Ray Chandler_, Jun 22 2003, Aug 03 2003