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 A141311 #22 Jul 20 2025 15:02:30
%S A141311 19,29,59,79,89,199,499,599,1999,2999,4999,8999,49999,59999,79999,
%T A141311 199999,599999,799999,2999999,4999999,19999999,29999999,59999999,
%U A141311 89999999,799999999,59999999999,79999999999,59999999999999,499999999999999,29999999999999999999
%N A141311 Primes consisting of a digit and a nonempty string of 9's (i.e., primes of the form k*10^m - 1, where k is any digit).
%C A141311 k can never be 1, 4, or 7, because if it were, k*10^m - 1 would be divisible by 3.
%H A141311 Jon E. Schoenfield, <a href="/A141311/b141311.txt">Table of n, a(n) for n = 1..71</a> (next term is 8*10^1219 - 1)
%t A141311 d={9};s={};Do[Do[m=FromDigits[Join[IntegerDigits[i],d]];If[PrimeQ[m],AppendTo[s,m]],{i,8}];AppendTo[d,9],{j,19}];s (* _James C. McMahon_, Jul 20 2025 *)
%Y A141311 Cf. A055558, A065582.
%K A141311 base,nonn
%O A141311 1,1
%A A141311 _Lekraj Beedassy_, Aug 02 2008
%E A141311 59999999 from Howard Berman (howard_berman(AT)hotmail.com), Apr 22 2009
%E A141311 Two more terms from _Jon E. Schoenfield_, Jan 12 2019