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 A143147 #5 Apr 09 2014 10:15:21 %S A143147 2,10,50,150,3150,9450,141750,850500,11056500,154791000,773955000, %T A143147 41019615000,1066509990000,3199529970000,15997649850000, %U A143147 239964747750000,2399647477500000,43193654595000000,2893974857865000000 %N A143147 a(1)=2. a(n) = the smallest positive multiple of a(n-1) that is > a(n-1) and has the same number of 0's as 1's in its binary representation. %Y A143147 Cf. A031443, A143146. %K A143147 base,nonn %O A143147 1,1 %A A143147 _Leroy Quet_, Jul 27 2008 %E A143147 a(5)-a(19) from _Donovan Johnson_, Sep 03 2008