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 A304168 #19 May 11 2018 03:08:25 %S A304168 5,16,50,154,470,1426,4310,12994,39110,117586,353270,1060834,3184550, %T A304168 9557746,28681430,86060674,258214790,774709906,2324260790,6973044514, %U A304168 20919657830,62760022066,188282163350,564850684354,1694560441670,5083698102226,15251127861110,45753450692194,137260486294310,411781727318386 %N A304168 a(n) = 2*3^n - 2^(n-1) (n>=1). %C A304168 For n>=2, a(n) is the number of edges of the Sierpinski Gasket Rhombus graph SR(n) (see Theorem 2.1 in the D. Antony Xavier et al. reference). %H A304168 Colin Barker, <a href="/A304168/b304168.txt">Table of n, a(n) for n = 1..1000</a> %H A304168 D. Antony Xavier, M. Rosary, and Andrew Arokiaraj, <a href="https://www.ijmsc.com/index.php/ijmsc/article/view/261">Topological properties of Sierpinski Gasket Rhombus graphs</a>, International J. of Mathematics and Soft Computing, 4, No. 2, 2014, 95-104. %H A304168 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5,-6). %F A304168 From _Colin Barker_, May 10 2018: (Start) %F A304168 G.f.: x*(5 - 9*x) / ((1 - 2*x)*(1 - 3*x)). %F A304168 a(n) = 5*a(n-1) - 6*a(n-2) for n>2. %F A304168 (End) %p A304168 seq(2*3^n-2^(n-1), n = 1 .. 40); %o A304168 (PARI) Vec(x*(5 - 9*x) / ((1 - 2*x)*(1 - 3*x)) + O(x^30)) \\ _Colin Barker_, May 10 2018 %o A304168 (GAP) List([1..35],n->2*3^n-2^(n-1)); # _Muniru A Asiru_, May 10 2018 %Y A304168 Cf. A304167, A304169, A304170. %K A304168 nonn,easy %O A304168 1,1 %A A304168 _Emeric Deutsch_, May 10 2018