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 A263404 #29 Aug 30 2019 06:11:08
%S A263404 25,324,3025,35721,11730625,71132356,1132591716,17136119025,
%T A263404 1923311317225,58191311792329,58191311792329,231372178511929,
%U A263404 1722376411319529,1134152319174379129,472643754131992311729,17298113195343723473641,419723711317595314724329,4319231361106417537475929
%N A263404 Smallest square containing the first n primes as substrings.
%C A263404 The sequence is infinite.
%e A263404 a(6) = 71132356 = 8464^2 contains 2, 3, 5, 7, 11 and 13 as substrings and no smaller square has that property.
%t A263404 Do[k = 1; While[! AllTrue[Prime@ Range@ n, StringContainsQ[ToString[k^2], ToString@ #] &], k++]; Print[k^2], {n, 9}] (* _Michael De Vlieger_, Oct 19 2015, Version 10 *)
%Y A263404 Cf. A054261, A069600.
%K A263404 nonn,base
%O A263404 1,1
%A A263404 _Emmanuel Vantieghem_, Oct 17 2015
%E A263404 a(15)-a(16) from _Bert Dobbelaere_, Oct 28 2018
%E A263404 a(17)-a(18) from _Giovanni Resta_, Aug 27 2019