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 A073140 #7 Mar 30 2012 18:50:25 %S A073140 0,2,4,6,8,11,11,14,16,21,21,25,21,25,25,30,32,41,41,47,41,47,47,53, %T A073140 41,47,47,53,47,53,53,62,64,81,81,91,81,91,91,99,81,91,91,99,91,99,99, %U A073140 109,81,91,91,99,91,99,99,109,91,99,99,109,99,109,109,126,128,161,161,179 %N A073140 Sum of the largest and smallest number having in binary representation the same number of 0's and 1's as n. %C A073140 a(n) = A073137(n) + A073138(n). %H A073140 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a> %Y A073140 Cf. A007088, A073139, A073141. %K A073140 nonn %O A073140 0,2 %A A073140 _Reinhard Zumkeller_, Jul 16 2002