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 A077858 #11 Mar 13 2021 07:59:09
%S A077858 1,3,5,7,11,19,31,47,71,111,175,271,415,639,991,1535,2367,3647,5631,
%T A077858 8703,13439,20735,31999,49407,76287,117759,181759,280575,433151,
%U A077858 668671,1032191,1593343,2459647,3796991,5861375,9048063,13967359,21561343,33284095,51380223
%N A077858 Expansion of (1-x)^(-1)/(1-2*x+2*x^2-2*x^3).
%H A077858 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (3,-4,4,-2).
%F A077858 a(n)-a(n-1) = A077943(n). - _R. J. Mathar_, Mar 13 2021
%t A077858 CoefficientList[Series[(1-x)^(-1)/(1-2x+2x^2-2x^3), {x,0,40}], x] (* _Harvey P. Dale_, Mar 31 2011 *)
%Y A077858 Cf. A077943.
%K A077858 nonn,easy
%O A077858 0,2
%A A077858 _N. J. A. Sloane_, Nov 17 2002