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 A151912 #5 Jun 13 2015 00:52:44 %S A151912 1,-4,-28,-56,32,416,832,-256,-4864,-9728,2048,51200,102400,-16384, %T A151912 -507904,-1015808,131072,4849664,9699328,-1048576,-45088768,-90177536, %U A151912 8388608,411041792,822083584,-67108864,-3690987520,-7381975040 %N A151912 Expansion of (1-8x-8x^3)/(1-2x+4x^2)^2. %C A151912 2*a(n) is the Hankel transform of A066796. %H A151912 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-12,16,-16). %F A151912 a(n)=2^n*A138341(n); %K A151912 easy,sign %O A151912 0,2 %A A151912 _Paul Barry_, Mar 15 2008