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 A158453 #16 Feb 22 2023 21:06:55 %S A158453 1,23,431,7857,142625,2587279,46929343,851213073,15439417633, %T A158453 280042119887,5079439221503,92131506968913,1671092849279201, %U A158453 30310492056413839,549775513106272063,9971897330025100689,180871526632046468257,3280670474584477332047,59505213248435614382975 %N A158453 Number of connected spanning subgraphs in 3 X n grid. %H A158453 Alois P. Heinz, <a href="/A158453/b158453.txt">Table of n, a(n) for n = 1..250</a> %H A158453 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (22,-73,54,-8). %F A158453 G.f.: (2*x^3-x^2-x) / (54*x^3-73*x^2-1+22*x-8*x^4). %p A158453 a:= n-> (Matrix([[23, 1, 0, 1/4]]). Matrix(4, (i, j)-> `if`(i=j-1, 1, %p A158453 `if`(j=1, [22, -73, 54, -8][i], 0)))^n)[1, 3]: %p A158453 seq(a(n), n=1..20); %Y A158453 Column k=3 of A359993. %K A158453 nonn,easy %O A158453 1,2 %A A158453 _Alois P. Heinz_, Mar 19 2009