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 A199993 #15 Feb 16 2025 08:33:16
%S A199993 39,49,55,57,66,68,69,74,75,78,86,87,88,93,94,95,96,98,147,155,159,
%T A199993 166,168,169,174,175,178,186,187,188,189,194,195,196,198,236,238,246,
%U A199993 247,248,249,264,266,267,272,274,276,279,284,288,289,292,294,297,298,299
%N A199993 Composite numbers whose multiplicative persistence is 3.
%C A199993 Complement of A046503 with respect to A046512.
%H A199993 Harvey P. Dale, <a href="/A199993/b199993.txt">Table of n, a(n) for n = 1..1000</a>
%H A199993 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MultiplicativePersistence.html">Multiplicative Persistence</a>
%F A199993 { A046512 } minus { A046503 }.
%e A199993 147 -> 1 * 4 * 7 -> [ 28 ] -> 2 * 8 -> [ 16 ] -> 1 * 6 -> [ 6 ] -> one digit in three steps.
%t A199993 Select[Range[300],CompositeQ[#]&&Length[NestWhileList[Times@@ IntegerDigits[ #]&,#,#>9&]] == 4&] (* _Harvey P. Dale_, Mar 29 2023 *)
%Y A199993 Cf. A046503 (primes whose multiplicative persistence is 3).
%K A199993 nonn,base
%O A199993 1,1
%A A199993 _Jaroslav Krizek_, Nov 13 2011