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 A214530 #9 Aug 30 2016 18:29:15
%S A214530 17,71,1177,1717,1771,7117,7171,7711,111777,117177,117717,117771,
%T A214530 171177,171717,171771,177117,177171,177711,711177,711717,711771,
%U A214530 717117,717171,717711,771117,771171,771711,777111
%N A214530 List of words over {1,7} with equal numbers of 1's and 7's.
%C A214530 This is to 7 as A214524 is to 6, as A214522 is to 5, as A214521 is to 4, as A214488 is to 3, and as A214218 is to 2. The subsequence of primes (when interpreted as decimal integers) is A087514.
%t A214530 Sort[FromDigits/@Flatten[Table[Permutations[PadRight[{},2n,{1,7}]],{n,3}],1]] (* _Harvey P. Dale_, Aug 30 2016 *)
%Y A214530 Cf. A214218, A214488, A214521, A214522, A214524.
%K A214530 nonn,base,easy
%O A214530 1,1
%A A214530 _Jonathan Vos Post_, Jul 20 2012