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 A173771 #10 Sep 08 2022 08:45:50
%S A173771 3,7,47,4447,4444444447,44444444444444444447,
%T A173771 44444444444444444444444447
%N A173771 Primes of form (4*10^n+23)/9.
%C A173771 a(9) has 1310 digits. - _Bruno Berselli_, Jul 26 2012
%H A173771 Vincenzo Librandi, <a href="/A173771/b173771.txt">Table of n, a(n) for n = 1..8</a>
%t A173771 Select[Table[(4*10^n+23)/9,{n,0,100}],PrimeQ] (* _Vincenzo Librandi_, Jul 26 2012 *)
%o A173771 (Magma) [a: n in [0..100] | IsPrime(a) where a is (4*10^n+23)div 9 ]; // _Vincenzo Librandi_, Jul 26 2012
%Y A173771 Cf. A173772
%Y A173771 Equals 3 followed by A092480 (primes of the form 40*R_n + 7). - _Klaus Brockhaus_ and _R. J. Mathar_, Feb 27 2010
%Y A173771 Cf. A056682.
%K A173771 nonn
%O A173771 1,1
%A A173771 _Vincenzo Librandi_, Feb 24 2010