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 A104146 #6 Oct 02 2013 15:12:45
%S A104146 1,3,1,1,3,1,1,147,17,1,3,7,1,297,1
%N A104146 Smallest k>0 such that n*10^k + k is prime.
%C A104146 (a(n) mod 10) in {1,3,7,9}.
%C A104146 a(16), if it exists, is greater than 20000. - _Ryan Propper_, Jul 21 2006
%C A104146 a(16), if it exists, is greater than 42000. - _Ryan Propper_, Sep 25 2006
%Y A104146 a(floor(A030430(n)/10)) = 1.
%K A104146 nonn,more
%O A104146 1,2
%A A104146 _Reinhard Zumkeller_, Mar 07 2005