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 A054256 #10 Oct 20 2019 17:27:11
%S A054256 7,33,169,197,209,351,401,419,459,541,553,599,883,971,981,1081,1107,
%T A054256 1201,1351,1363,2011,2321,2347,2563,2607,2679,2703,2861,2869,2909,
%U A054256 2959,3033,3067,3177,3333,3403,3437,3461,3471,3513,3601,3647,3769,3821,3833
%N A054256 Concatenation of n in base 2 up to base 10 is prime, all numbers are interpreted as decimals.
%H A054256 Harvey P. Dale, <a href="/A054256/b054256.txt">Table of n, a(n) for n = 0..1000</a>
%e A054256 a(1)=7 -> 111{2}=21{3}=13{4}=12{5}=11{6}=10{7}=7{8}=7{9}=7{10} -> 1112113121110777 is a prime.
%t A054256 Select[Range[4000],PrimeQ[FromDigits[Flatten[Table[IntegerDigits[#,n],{n,2,10}]]]]&] (* _Harvey P. Dale_, Aug 20 2017 *)
%Y A054256 Cf. A054257, A054258.
%K A054256 nonn,base
%O A054256 0,1
%A A054256 _Patrick De Geest_, Feb 15 2000