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 A090153 #7 May 31 2020 12:48:10
%S A090153 5,53,59,577,599,5333,59999,511111,599999,59999999,577777777,
%T A090153 59999999999,5111111111111,53333333333333,59999999999999,
%U A090153 577777777777777,5111111111111111,577777777777777777
%N A090153 Primes of the form identical digits preceded by a 5.
%H A090153 Vincenzo Librandi, <a href="/A090153/b090153.txt">Table of n, a(n) for n = 1..43</a>
%t A090153 Select[ FromDigits /@ Flatten[ Table[ PadRight[{5}, i, # ] & /@ {1, 2, 3, 4, 5, 6, 7, 8, 9}, {i, 2, 24}], 1], PrimeQ[ # ] &]
%t A090153 Join[{5},Select[Flatten[Table[FromDigits[PadRight[{5},n,k]],{n,2,20},{k,{1,3,7,9}}]],PrimeQ]] (* _Harvey P. Dale_, May 31 2020 *)
%K A090153 nonn,base
%O A090153 1,1
%A A090153 _Robert G. Wilson v_, Nov 22 2003