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 A073730 #11 Jan 27 2014 12:30:21
%S A073730 11,22,33,44,55,66,77,88,99,10,11,21,31,41,51,61,71,81,91,20,21,22,32,
%T A073730 42,52,62,72,82,92,30,31,32,33,43,53,63,73,83,93,40,41,42,43,44,54,64,
%U A073730 74,84,94,50,51,52,53,54,55,65,75,85,95,60,61,62,63,64,65,66,76,86,96
%N A073730 Concatenation of largest and smallest digits of n in decimal representation.
%C A073730 10 <= a(n) <= 99; a(a(n))=a(n).
%H A073730 Reinhard Zumkeller, <a href="/A073730/b073730.txt">Table of n, a(n) for n = 1..10000</a>
%F A073730 a(n) = A054055(n)*10 + A054054(n).
%e A073730 a(12321)=31; a(3210123)=30; a(59387)=83; a(8923)=92.
%t A073730 Table[FromDigits[{Max[x = IntegerDigits[n]], Min[x]}], {n, 69}] (* _Jayanta Basu_, Jul 08 2013 *)
%o A073730 (Haskell)
%o A073730 a073730 n = 10 * a054055 n + a054054 n
%o A073730 -- _Reinhard Zumkeller_, Jul 21 2013
%Y A073730 Cf. A073729.
%K A073730 nonn,base,look
%O A073730 1,1
%A A073730 _Reinhard Zumkeller_, Aug 05 2002