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 A046453 #15 Jun 20 2021 02:29:10
%S A046453 16,81,625,2401,3975,4719,5565,6591,8745,10731,14399,14641,16863,
%T A046453 20111,34391,36501,39963,41019,46179,47229,48231,60813,61761,62991,
%U A046453 69027,109179,113631,116475,143991,158985,159777,162409,164145,167571,183159,184065
%N A046453 Composite numbers with four prime factors (not necessarily distinct) whose concatenation yields a palindrome.
%e A046453 164145 = 3 * 5 * 31 * 353 -> 3531353 is palindromic.
%t A046453 pal4Q[n_]:=Module[{ds=Flatten[IntegerDigits/@(Table[First[#],{Last[ #]}]&/@ FactorInteger[n])]},PrimeOmega[n]==4&&ds==Reverse[ds]]; Select[ Range[190000],pal4Q] (* _Harvey P. Dale_, Nov 12 2011 *)
%Y A046453 Intersection of A033993 and A046447.
%K A046453 nonn,base
%O A046453 1,1
%A A046453 _Patrick De Geest_, Jul 15 1998
%E A046453 One more term from _Harvey P. Dale_, Nov 12 2011