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 A103749 #12 Jun 13 2015 00:51:46
%S A103749 0,1,1,-2,3,1,-8,13,-3,-26,55,-35,-72,217,-215,-146,795,-1079,-8,2677,
%T A103749 -4827,2134,8047,-19835,16056,19873,-75599,87838,27507,-266543,414712,
%U A103749 -93155,-854643,1777222,-1108889,-2377619,7040952,-6881111,-4915079,25878094,-34725237,-983015
%N A103749 Expansion of x*(1+2*x)/(1+x+x^2-2*x^3).
%C A103749 Insert n=3, p=2, q=-1 and r=1 in Kenyon's characteristic polynomial x^n-p*x^(n-1)+q*x+r=0 .
%H A103749 Richard Kenyon, <a href="http://arXiv.org/abs/math.MG/9505210">The Construction of Self-Similar Tilings</a>, arXiv:math.MG/9405210
%H A103749 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-1,2).
%F A103749 a(n) = -a(n-1)-a(n-2)+2*a(n-3) = A077975(n-1)+2*A077975(n-2).
%t A103749 LinearRecurrence[{-1,-1,2},{0,1,1},50] (* _Harvey P. Dale_, Jul 23 2013 *)
%Y A103749 Cf. A099206.
%K A103749 sign,easy
%O A103749 0,4
%A A103749 _Roger L. Bagula_, Mar 28 2005
%E A103749 Edited, replaced by signed variant by the Assoc. Eds. of the OEIS - Jul 31 2010