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 A222728 #6 Nov 07 2021 13:43:33
%S A222728 77,707,717,737,747,767,777,7007,7117,7227,7337,7447,7557,7667,7777,
%T A222728 7887,7997,70007,70107,70307,70407,70707,70807,70907,71017,71117,
%U A222728 71217,71417,71517,71617,71717,71817,72027,72127,72327,72427,72527,72627,72827,72927,73137
%N A222728 Palindromic composite numbers starting with a digit 7.
%C A222728 Subsequence of A032350 (palindromic nonprime numbers) and A002113 (palindromic numbers). Complement of A222727 (palindromic primes starting with a digit 7) with respect to A043042 (palindromic numbers starting with a digit 7).
%H A222728 Jaroslav Krizek, <a href="/A222728/b222728.txt">Table of n, a(n) for n = 1..1038</a>
%t A222728 Table[Select[Range[7*10^d,8*10^d-1],CompositeQ[#]&&PalindromeQ[#]&],{d,4}]//Flatten (* _Harvey P. Dale_, Nov 07 2021 *)
%Y A222728 Cf. A032350, A002113, A222727, A043042.
%K A222728 nonn,base
%O A222728 1,1
%A A222728 _Jaroslav Krizek_, Mar 09 2013