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 A003769 #23 Jan 01 2019 06:31:05 %S A003769 3,16,75,361,1728,8281,39675,190096,910803,4363921,20908800,100180081, %T A003769 479991603,2299777936,11018898075,52794712441,252954664128, %U A003769 1211978608201,5806938376875,27822713276176,133306628004003,638710426743841,3060245505715200 %N A003769 Number of perfect matchings (or domino tilings) in K_4 X P_n. %D A003769 F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Ars Combin. 49 (1998), 129-154. %H A003769 Colin Barker, <a href="/A003769/b003769.txt">Table of n, a(n) for n = 1..1000</a> %H A003769 F. Faase, <a href="http://www.iwriteiam.nl/Cpaper.zip">On the number of specific spanning subgraphs of the graphs G X P_n</a>, Preliminary version of paper that appeared in Ars Combin. 49 (1998), 129-154. %H A003769 F. Faase, <a href="http://www.iwriteiam.nl/counting.html">Counting Hamiltonian cycles in product graphs</a> %H A003769 F. Faase, <a href="http://www.iwriteiam.nl/Cresults.html">Results from the counting program</a> %H A003769 <a href="/index/Do#domino">Index entries for sequences related to dominoes</a> %H A003769 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,4,-1). %F A003769 a(n) = 4a(n-1) + 4a(n-2) - a(n-3), n>3. %F A003769 a(n) = (1/7)*(6*A030221(n) - A054477(n) + 2(-1)^n). %F A003769 G.f.: x*(3+4*x-x^2)/((1+x)*(1-5*x+x^2)). - _R. J. Mathar_, Dec 16 2008 %F A003769 a(n) = 2^(-1-n)*((-1)^n*2^(2+n) + (5-sqrt(21))^(1+n) + (5+sqrt(21))^(1+n)) / 7. - _Colin Barker_, Dec 16 2017 %o A003769 (PARI) Vec(x*(3 + 4*x - x^2) / ((1 + x)*(1 - 5*x + x^2)) + O(x^40)) \\ _Colin Barker_, Dec 16 2017 %Y A003769 Essentially the same as A005386. First differences of A099025. %K A003769 nonn,easy %O A003769 1,1 %A A003769 _Frans J. Faase_