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 A226546 #17 Sep 05 2021 22:00:27 %S A226546 0,3,12,34,98,256,654,1625,3964,9533,22662,53373,124728,289572,668514, %T A226546 1535869,3513614,8008090,18191184,41200568,93064834,209710139, %U A226546 471520566,1058065647,2369890254,5299215579,11830941840,26375563624,58722396932,130576680919 %N A226546 Number of squares in all tilings of a 3 X n rectangle using integer-sided square tiles. %H A226546 Alois P. Heinz, <a href="/A226546/b226546.txt">Table of n, a(n) for n = 0..1000</a> %H A226546 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (2,3,-2,-6,-4,-1). %F A226546 G.f.: (x^2+6*x+3)*x/(x^3+2*x^2+x-1)^2. %F A226546 a(n) = 2*a(n-1) + 3*a(n-2) - 2*a(n-3) - 6*a(n-4) - 4*a(n-5) - a(n-6) for n>5. - _Colin Barker_, Jun 07 2020 %o A226546 (PARI) concat(0, Vec(x*(3 + 6*x + x^2) / (1 - x - 2*x^2 - x^3)^2 + O(x^30))) \\ _Colin Barker_, Jun 07 2020 %Y A226546 Column k=3 of A226545. %Y A226546 Cf. A002478. %K A226546 nonn,easy %O A226546 0,2 %A A226546 _Alois P. Heinz_, Jun 10 2013