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 A121044 #4 Apr 02 2025 19:01:08 %S A121044 7,89,983,9931,99991,999331,9997879,99999551,999998693,9999995363, %T A121044 99999976319,999999998533,9999999954787 %N A121044 Greatest cluster prime less than 10^n. %C A121044 These numbers are useful for generating intermediate cluster primes because the best algorithm for generating cluster primes requires starting with a known cluster prime. %H A121044 Wikipedia, <a href="https://en.wikipedia.org/wiki/Cluster_prime">Cluster prime</a>. %Y A121044 Cf. A038134 (cluster primes), A039506 (number of cluster primes < 10^n), A121045. %K A121044 nonn %O A121044 1,1 %A A121044 _T. D. Noe_, Jul 21 2006