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 A137206 #10 Jan 16 2017 03:24:00 %S A137206 0,2,-1,4,-2,8,-4,16,-8,32,-16,64,-32,128,-64,256,-128,512,-256,1024, %T A137206 -512,2048,-1024,4096,-2048,8192,-4096,16384,-8192,32768,-16384,65536, %U A137206 -32768,131072,-65536,262144,-131072,524288,-262144,1048576,-524288 %N A137206 First differences of A074323. %H A137206 Matthew House, <a href="/A137206/b137206.txt">Table of n, a(n) for n = 0..6605</a> %H A137206 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,2). %F A137206 From _R. J. Mathar_, Apr 22 2009: (Start) %F A137206 G.f.: x*(2-x)/(1-2*x^2). %F A137206 a(n) = (-1)^(n+1)*A135530(n-1). (End) %F A137206 a(n) = 2*a(n-2). - _Matthew House_, Jan 15 2017 %Y A137206 Cf. A000079, A131577, A135530. %K A137206 sign %O A137206 0,2 %A A137206 _Paul Curtz_, Mar 05 2008 %E A137206 More terms from _R. J. Mathar_, Apr 22 2009