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 A214209 #9 Jul 09 2012 10:52:21 %S A214209 1,3,5,10,21,41,83,165,330,661,1321,2642,5285,10569,21139,42277,84554, %T A214209 169109,338217,676435,1352869,2705738,5411477,10822953,21645906, %U A214209 43291813,86583625,173167251,346334501,692669002,1385338005,2770676009,5541352018,11082704037,22165408073,44330816147,88661632293,177323264586,354646529173,709293058345 %N A214209 Numbers appearing in A214208 excluding powers 2^i with i>0. %C A214209 Created with the hope of obtaining a better understanding of A213975. %F A214209 It appears that a(n+1) = 2*a(n) + eps, where eps = 0, 1 or -1. The first 130 values of eps show a pattern which is somewhat mysterious. %Y A214209 Cf. A213975, A214207, A214208. %K A214209 nonn %O A214209 1,2 %A A214209 _N. J. A. Sloane_, Jul 09 2012