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 A170939 #7 Jul 28 2015 16:39:23 %S A170939 2,4,14,58,242,994,4034,16258,65282,261634,1047554,4192258,16773122, %T A170939 67100674,268419074,1073709058,4294901762,17179738114,68719214594, %U A170939 274877382658,1099510579202,4398044413954,17592181850114,70368735789058,281474959933442,1125899873288194 %N A170939 4^n-2^n+2. %H A170939 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (7, -14, 8). %F A170939 a(n)= 7*a(n-1) -14*a(n-2) +8*a(n-3) = 2*A134169(n). G.f.: 2*(1-5*x+7*x^2)/((1-x) * (2*x-1) * (4*x-1)). [From _R. J. Mathar_, Feb 15 2010] %K A170939 nonn %O A170939 0,1 %A A170939 _N. J. A. Sloane_, Feb 13 2010