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 A304168 a(n) = 2*3^n - 2^(n-1) (n>=1). 2
 5, 16, 50, 154, 470, 1426, 4310, 12994, 39110, 117586, 353270, 1060834, 3184550, 9557746, 28681430, 86060674, 258214790, 774709906, 2324260790, 6973044514, 20919657830, 62760022066, 188282163350, 564850684354, 1694560441670, 5083698102226, 15251127861110, 45753450692194, 137260486294310, 411781727318386 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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). LINKS Colin Barker, Table of n, a(n) for n = 1..1000 D. Antony Xavier, M. Rosary, and Andrew Arokiaraj, Topological properties of Sierpinski Gasket Rhombus graphs, International J. of Mathematics and Soft Computing, 4, No. 2, 2014, 95-104. Index entries for linear recurrences with constant coefficients, signature (5,-6). FORMULA From Colin Barker, May 10 2018: (Start) G.f.: x*(5 - 9*x) / ((1 - 2*x)*(1 - 3*x)). a(n) = 5*a(n-1) - 6*a(n-2) for n>2. (End) MAPLE seq(2*3^n-2^(n-1), n = 1 .. 40); PROG (PARI) Vec(x*(5 - 9*x) / ((1 - 2*x)*(1 - 3*x)) + O(x^30)) \\ Colin Barker, May 10 2018 (GAP) List([1..35], n->2*3^n-2^(n-1)); # Muniru A Asiru, May 10 2018 CROSSREFS Cf. A304167, A304169, A304170. Sequence in context: A007806 A037480 A027108 * A317817 A077840 A007343 Adjacent sequences:  A304165 A304166 A304167 * A304169 A304170 A304171 KEYWORD nonn,easy AUTHOR Emeric Deutsch, May 10 2018 STATUS approved

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Last modified April 25 16:59 EDT 2019. Contains 322461 sequences. (Running on oeis4.)