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 A036307 #26 May 18 2022 07:56:17
%S A036307 49,77,119,121,187,289,343,497,539,781,833,847,1207,1309,1331,2023,
%T A036307 2057,2401,3179,3479,3773,4913,5041,5467,5831,5929,7819,8197,8449,
%U A036307 8591,9163,9317,12287,12439,12881,13277,14161,14399,14641,16807,18989,19547
%N A036307 Composite numbers whose prime factors contain no digits other than 1 and 7.
%C A036307 All terms are a product of at least two terms of A020455. - _David A. Corneth_, Oct 09 2020
%H A036307 David A. Corneth, <a href="/A036307/b036307.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Alois P. Heinz)
%H A036307 <a href="/index/Pri#prime_factors">Index entries for sequences related to prime factors</a>.
%F A036307 Sum_{n>=1} 1/a(n) = Product_{p in A020455} (p/(p - 1)) - Sum_{p in A020455} 1/p - 1 = 0.0775663737... . - _Amiram Eldar_, May 18 2022
%Y A036307 Cf. A003599, A020455, A036302-A036325.
%K A036307 nonn,easy,base
%O A036307 1,1
%A A036307 _Patrick De Geest_, Dec 15 1998