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 A214531 #8 Jan 17 2014 15:59:13
%S A214531 18,81,1188,1818,1881,8118,8181,8811,111888,118188,118818,118881,
%T A214531 181188,181818,181881,188118,188181,188811,811188,811818,811881,
%U A214531 818118,818181,818811,881118,881181,881811,888111
%N A214531 List of words over {1,8} with equal numbers of 1's and 8's.
%C A214531 This is to 8 as A214530 is to 7, as A214530 is to 6, as A214522 is to 5, as A214521 is to 4, as A214488 is to 3, and as A214218 is to 2. All of these, interpreted as decimal integers are divisible by 9, because each pair of "1" and "8" contributes a digital sum of 9, hence the total is divisible by 9.
%H A214531 Harvey P. Dale, <a href="/A214531/b214531.txt">Table of n, a(n) for n = 1..1000</a>
%t A214531 With[{tb=Table[Join[PadRight[{},n,1],PadRight[{},n,8]],{n,3}]},FromDigits/@ Flatten[Permutations/@tb,1]] (* _Harvey P. Dale_, Jan 17 2014 *)
%Y A214531 Cf. A214218, A214488, A214521, A214522, A214524, A214530.
%K A214531 nonn,base,easy
%O A214531 1,1
%A A214531 _Jonathan Vos Post_, Jul 20 2012