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 A100490 #7 Sep 01 2024 14:52:57
%S A100490 1,9,21,27,33,39,49,51,57,63,69,77,81,87,91,93,99,111,117,119,121,123,
%T A100490 129,133,141,143,147,153,159,161,169,171,177,183,187,189,201,203,207,
%U A100490 209,213,217,219,221,231,237,243,247,249,253,259,261,267,273,279,287
%N A100490 Odd numbers ending in {1,3,7,9} that are not primes.
%C A100490 Essentially the same as A053795. [From _R. J. Mathar_, Sep 02 2008]
%t A100490 Select[Range[1,311,2],MemberQ[{1,3,7,9},Mod[#,10]]&&!PrimeQ[#]&] (* _Harvey P. Dale_, Sep 01 2024 *)
%K A100490 nonn
%O A100490 0,2
%A A100490 _Roger L. Bagula_, Nov 22 2004