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 A020874 #23 Jul 08 2025 07:56:54
%S A020874 0,3,30,135,452,1295,3378,8295,19560,44847,100790,223223,488940,
%T A020874 1061775,2289882,4910535,10480208,22275695,47178270,99605847,
%U A020874 209704980,440390223,922733570,1929364775,4026514872
%N A020874 Number of paths in Moebius ladder M_n.
%D A020874 J. P. McSorley, Counting structures in the Moebius ladder, Discrete Math., 184 (1998), 137-164.
%H A020874 Vincenzo Librandi, <a href="/A020874/b020874.txt">Table of n, a(n) for n = 0..1000</a>
%H A020874 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (8,-26,44,-41,20,-4).
%F A020874 a(n) = 10*n*2^n-n^3-5*n^2-11*n.
%F A020874 G.f.: -x*(8*x^4-20*x^3+27*x^2-6*x-3) / ((x-1)^4*(2*x-1)^2). - _Colin Barker_, Apr 05 2013
%t A020874 CoefficientList[Series[- x (8 x^4 - 20 x^3 + 27 x^2 - 6 x - 3)/((x - 1)^4 (2*x - 1)^2), {x, 0, 30}], x] (* _Vincenzo Librandi_, Oct 16 2013 *)
%t A020874 LinearRecurrence[{8,-26,44,-41,20,-4},{0,3,30,135,452,1295},30] (* _Harvey P. Dale_, Apr 05 2018 *)
%o A020874 (Magma) [10*n*2^n-n^3-5*n^2-11*n: n in [0..30]]; // _Vincenzo Librandi_, Oct 16 2013
%K A020874 nonn,easy
%O A020874 0,2
%A A020874 _N. J. A. Sloane_