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 A387093 #13 Aug 17 2025 02:54:58 %S A387093 25,27,32,35,72,75,222,225,252,322,333,375,525,552,555,575,735,777, %T A387093 2352,2553,2555,2775,3357,3375,3552,3577,5222,5352,5575,7252,7322, %U A387093 23253,23373,23532,23535,23552,25275,25725,25737,27232,27252,27375,32352,32375 %N A387093 Composite numbers that contain only prime digits and whose prime factors contain only prime digits. %H A387093 Scott R. Shannon, <a href="/A387093/b387093.txt">Table of n, a(n) for n = 1..2298</a> (all terms < 10^12). %e A387093 25725 is a term as 25725 = 3 * 5^2 * 7^3, and both the number and its prime factors only contain prime digits. %t A387093 Select[Select[Range[33000], CompositeQ], And[AllTrue[Union@ IntegerDigits[#], PrimeQ], AllTrue[Union@ Flatten@ Map[IntegerDigits, FactorInteger[#][[All, 1]] ], PrimeQ]] &] (* _Michael De Vlieger_, Aug 16 2025 *) %Y A387093 Cf. A061371, A027746, A000040, A019546. %K A387093 nonn,base %O A387093 1,1 %A A387093 _Scott R. Shannon_ and Ursula Ponting, Aug 16 2025