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 A287534 #15 Jun 02 2017 00:33:28
%S A287534 9,33,39,77,91,93,99,111,113,117,119,133,171,177,319,333,339,371,377,
%T A287534 391,393,399,711,713,717,731,737,771,777,779,791,793,799,913,917,931,
%U A287534 933,939,973,979,993,999
%N A287534 Composite numbers whose digits are restricted to 1, 3, 7, and 9.
%t A287534 Select[Flatten@ Array[FromDigits /@ Tuples[{1, 3, 7, 9}, #] &, 3], CompositeQ] (* _Michael De Vlieger_, Jun 01 2017 *)
%Y A287534 Cf. A091633, A136333.
%K A287534 nonn,base
%O A287534 1,1
%A A287534 _Luke Zieroth_, May 26 2017