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 A383934 #9 Aug 23 2025 10:02:03 %S A383934 1111,1199,1681,1691,1919,1991,4141,4411,4469,4499,4609,4961,6109, %T A383934 6161,6611,6649,6809,8899,8989,9089,9481,9691,10109,10901,11009,11041, %U A383934 11099,11419,11881,14641,14801,16109,16441,16489,16999,18409,18491,18601,18689 %N A383934 Composite numbers that contain only nonprime digits and whose prime factors contain only nonprime digits. %H A383934 Scott R. Shannon, <a href="/A383934/b383934.txt">Table of n, a(n) for n = 1..10000</a> %e A383934 10109 is a term as 10109 = 11 * 919, and both the number and its prime factors only contain nonprime digits. %t A383934 Select[Select[Range[20000], And[CompositeQ[#], NoneTrue[IntegerDigits[#], PrimeQ]] &], NoneTrue[Flatten[IntegerDigits /@ FactorInteger[#][[All, 1]] ], PrimeQ] &] (* _Michael De Vlieger_, Aug 23 2025 *) %Y A383934 Cf. A084984, A018252, A387093, A000040. %K A383934 nonn,base,new %O A383934 1,1 %A A383934 _Scott R. Shannon_, Aug 17 2025