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 A217783 #13 Oct 02 2023 13:50:02 %S A217783 1,5,21,83,318,1196,4445,16389,60097,219527,799734,2907800,10558041, %T A217783 38297573,138819053,502925211,1821362830,6594366404,23870720757, %U A217783 86396702117,312668994969,1131463798415,4094241931526,14814592074288,53603587025713,193949782284101 %N A217783 Expansion of (1-x)*(1-2x)/((1-5x+5*x^2)*(1-3x+x^2)). %C A217783 A diagonal of the square array A217770. %H A217783 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (8, -21, 20, -5). %F A217783 a(n) = A217770(n,n+3). %F A217783 a(n) = 8*a(n-1) -21*a(n-2) + 20*a(n-3) -5*a(n-4) for n>=4, a(0) = 1, a(1) = 5, a(2) = 21, a(3) = 83. %Y A217783 Cf. A217770, A217777, A217778, A217779, A217782. %K A217783 nonn,easy %O A217783 0,2 %A A217783 _Philippe Deléham_, Mar 24 2013