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 A176987 #27 Jul 08 2024 15:17:23
%S A176987 73,9973,9999973,99999999999973,99999999999999999973,
%T A176987 9999999999999999999973,99999999999999999999999999973,
%U A176987 9999999999999999999999999999973,9999999999999999999999999999999999999973
%N A176987 Primes of the form 10^n-27.
%H A176987 Vincenzo Librandi, <a href="/A176987/b176987.txt">Table of n, a(n) for n = 1..14</a>
%t A176987 Select[Table[10^n - 27, {n, 2, 500}], PrimeQ] (* _Vincenzo Librandi_, Jan 03 2014 *)
%t A176987 Select[Table[FromDigits[PadLeft[{7,3},n,9]],{n,2,40}],PrimeQ] (* _Harvey P. Dale_, Jul 08 2024 *)
%o A176987 (Magma) [a: n in [2..250]|IsPrime(a) where a is 10^n-27];
%Y A176987 Cf. A108329.
%K A176987 nonn
%O A176987 1,1
%A A176987 _Vincenzo Librandi_, Dec 11 2010