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 A036309 #29 May 18 2022 07:56:20
%S A036309 121,209,361,1331,2101,2189,2299,3629,3781,3971,6859,10021,10109,
%T A036309 10901,14641,17309,17461,18829,21989,23111,24079,25289,36481,37981,
%U A036309 38009,39601,39919,41591,43681,68951,71839,75449,101189,110231,111199,119911
%N A036309 Composite numbers whose prime factors contain no digits other than 1 and 9.
%C A036309 All terms are a product of at least two terms of A020457. - _David A. Corneth_, Oct 09 2020
%H A036309 David A. Corneth, <a href="/A036309/b036309.txt">Table of n, a(n) for n = 1..10000</a> (first 360 terms from Harvey P. Dale)
%H A036309 <a href="/index/Pri#prime_factors">Index entries for sequences related to prime factors</a>.
%F A036309 Sum_{n>=1} 1/a(n) = Product_{p in A020457} (p/(p - 1)) - Sum_{p in A020457} 1/p - 1 = 0.0200389643... . - _Amiram Eldar_, May 18 2022
%t A036309 Select[Range[120000],CompositeQ[#]&&SubsetQ[{1,9},Union[Flatten[ IntegerDigits /@ FactorInteger[ #][[All,1]]]]]&] (* _Harvey P. Dale_, Mar 30 2019 *)
%Y A036309 Cf. A020457, A036302-A036325.
%K A036309 nonn,easy,base
%O A036309 1,1
%A A036309 _Patrick De Geest_, Dec 15 1998