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 A046509 #15 Feb 16 2025 08:32:39 %S A046509 26899889,28698899,28699889,28869989,28889699,28899869,28989689, %T A046509 29868989,29888699,29968889,29988869,38849989,38894899,38898949, %U A046509 38899489,38984989,39849889,43898989,43988899,43989889,46668899 %N A046509 Primes with multiplicative persistence value 9. %H A046509 Daniel Mondot, <a href="/A046509/b046509.txt">Table of n, a(n) for n = 1..10000</a> %H A046509 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MultiplicativePersistence.html">Multiplicative Persistence</a> %e A046509 26899889 -> [ 4478976 ][ 338688 ][ 27648 ][ 2688 ][ 768 ][ 336 ][ 54 ][ 20 ][ 0 ] -> one digit in nine steps. %Y A046509 Intersection of A000040 and A046518. %Y A046509 Cf. A046500. %K A046509 nonn,base %O A046509 1,1 %A A046509 _Patrick De Geest_, Sep 15 1998