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 A105723 a(n) = 3^n - (-1)^n. 9
 0, 4, 8, 28, 80, 244, 728, 2188, 6560, 19684, 59048, 177148, 531440, 1594324, 4782968, 14348908, 43046720, 129140164, 387420488, 1162261468, 3486784400, 10460353204, 31381059608, 94143178828, 282429536480, 847288609444, 2541865828328, 7625597484988 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Muniru A Asiru, Table of n, a(n) for n = 0..2000 Dhroova Aiylam, Tanya Khovanova, Weighted Mediants and Fractals, arXiv:1711.01475 [math.NT], 2017. See p. 17. Index entries for linear recurrences with constant coefficients, signature (2,3). FORMULA a(n) = A102345(n) - 2*(-1)^n; (a(n) + A102345(n))/2 = A000244(n); A007814(a(n)) = A085058(n-1) for n > 0. E.g.f.: exp(3*x) - exp(-x). - G. C. Greubel, Nov 21 2018 G.f.: 4*x/((1+x)*(1-3*x)). - R. J. Mathar, Mar 08 2021 a(n) = 4*A015518(n). - R. J. Mathar, Mar 08 2021 MATHEMATICA LinearRecurrence[{2, 3}, {0, 4}, 30] (* Jean-François Alcover, Nov 11 2018 *) Table[3^n - (-1)^n, {n, 0, 30}] (* Vincenzo Librandi, Nov 21 2018 *) PROG (PARI) a(n) = 3^n - (-1)^n; \\ Michel Marcus, Aug 18 2017 (GAP) List([0..25], n->3^n-(-1)^n); # Muniru A Asiru, Nov 11 2018 (MAGMA) [3^n-(-1)^n: n in [0..30]]; // Vincenzo Librandi, Nov 21 2018 (Sage) [3^n - (-1)^n for n in range(30)] # G. C. Greubel, Nov 21 2018 CROSSREFS Cf. A000244, A102345. Cf. A007814, A085058. Sequence in context: A034515 A189546 A059480 * A280118 A143555 A025234 Adjacent sequences:  A105720 A105721 A105722 * A105724 A105725 A105726 KEYWORD nonn,easy AUTHOR Reinhard Zumkeller, Apr 18 2005 EXTENSIONS Corrected by T. D. Noe, Dec 11 2006 STATUS approved

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Last modified June 24 02:56 EDT 2021. Contains 345415 sequences. (Running on oeis4.)