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 A145852 #8 Mar 24 2020 08:43:39 %S A145852 109,2099,409999,1909999999999999999999, %T A145852 2809999999999999999999999999999, %U A145852 41099999999999999999999999999999999999999999,7609999999999999999999999999999999999999999999999999999999999999999999999999999 %N A145852 Primes of the form k followed by a 0 and k 9's. %C A145852 Primes of the form k*10^(k+1) + 10^k - 1. %o A145852 (PARI) lista(nn) = for(k=1, nn, if(ispseudoprime(q=k*10^(k+1)+10^k-1), print1(q, ", "))); \\ _Jinyuan Wang_, Mar 24 2020 %Y A145852 Cf. A141311, A145851. %K A145852 nonn %O A145852 1,1 %A A145852 _Lekraj Beedassy_, Oct 21 2008