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 A158450 #15 Feb 22 2023 21:02:26 %S A158450 1,4,112,3102,85818,2373870,65664106,1816344222,50242141946, %T A158450 1389754592846,38442187035914,1063354458854270,29413589398458778, %U A158450 813613216256931886,22505463603889302698,622526628016224886878,17219792020736937982522,476318961941184616298510 %N A158450 Number of spanning forests in 3 X n grid. %H A158450 Alois P. Heinz, <a href="/A158450/b158450.txt">Table of n, a(n) for n = 0..250</a> %H A158450 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (33,-154,176,-32). %F A158450 G.f.: (28*x^4-154*x^3+134*x^2-29*x+1)/(32*x^4-176*x^3+154*x^2-33*x+1). %e A158450 For n = 1 the a(1) = 4 forests are 1.2.3, 1-2.3, 1.2-3, 1-2-3. %p A158450 a:= n-> ceil((Matrix([[112, 4, 1/8, 0]]). Matrix(4, (i, j)-> if i=j-1 then 1 elif j=1 then [33, -154, 176, -32][i] else 0 fi)^n)[1, 3]): %p A158450 seq(a(n), n=0..20); %Y A158450 Row 3 of A360194. %K A158450 nonn,easy %O A158450 0,2 %A A158450 _Alois P. Heinz_, Mar 19 2009 %E A158450 a(0) inserted by _Alois P. Heinz_, Jan 23 2013