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 A177507 #20 Sep 08 2022 08:45:53
%S A177507 7,43,4003,40000003,40000000003,
%T A177507 40000000000000000000000000000000000000003
%N A177507 Primes of the form 4*10^n+3.
%C A177507 a(9) has 1738 digits. - _Vincenzo Librandi_, Jan 03 2014
%H A177507 Vincenzo Librandi, <a href="/A177507/b177507.txt">Table of n, a(n) for n = 1..8</a>
%H A177507 Makoto Kamada, <a href="https://stdkmd.net/nrr/4/40003.htm#prime">Prime numbers of the form 400...003</a>.
%t A177507 Select[Table[4 10^n + 3, {n, 0, 300}], PrimeQ] (* _Vincenzo Librandi_, Jan 03 2014 *)
%o A177507 (Magma) [a: n in [0..250] | IsPrime(a) where a is 4*10^n+3];
%Y A177507 Cf. A101397.
%K A177507 nonn
%O A177507 1,1
%A A177507 _Vincenzo Librandi_, Dec 11 2010