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 A036947 #14 Mar 09 2020 12:26:55 %S A036947 5,59,599,0,59999,599959,5595559,55555559,555555599,5555555959, %T A036947 55555595999,555555555559,5555555599999,55555555595599, %U A036947 555555555995959,5555555555559959,55555555555555999,555555555555555559 %N A036947 Smallest n-digit prime containing only the digits 5 and 9, or 0 if no such prime exists. %H A036947 Jinyuan Wang, <a href="/A036947/b036947.txt">Table of n, a(n) for n = 1..500</a> %Y A036947 Cf. A020468, A036229, A036321. %K A036947 nonn,base %O A036947 1,1 %A A036947 _Patrick De Geest_, Jan 04 1999