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 A187915 a(n) = (1/2)*((n+2)*P(n-1)+(5*n+1)*P(n)) where P() = A000129 are the Pell numbers. 1
 3, 13, 45, 141, 419, 1201, 3357, 9209, 24899, 66549, 176205, 462917, 1208163, 3135449, 8097597, 20823921, 53350531, 136228445, 346819437, 880594813, 2230476067, 5637208449, 14218682973, 35797815913, 89974587843, 225790779205, 565803994509, 1415938252341, 3539007315683, 8835146000809, 22033012367997, 54889789955297 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES R. P. Grimaldi, Ternary strings with no consecutive 0's and no consecutive 1's, Congressus Numerantium, 205 (2011), 129-149. (The sequence r_n) LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (4,-2,-4,-1) FORMULA G.f.: x*( 3+x-x^2-x^3 ) / (x^2+2*x-1)^2 . - R. J. Mathar, Mar 18 2011; adapted to the offset by Bruno Berselli, Apr 04 2011 MATHEMATICA CoefficientList[Series[(3 + x - x^2 - x^3) / (x^2 + 2 x - 1)^2, {x, 0, 40}], x] (* Vincenzo Librandi, Jun 19 2013 *) CROSSREFS Cf. A000129. Sequence in context: A212416 A058934 A141088 * A115128 A140420 A308087 Adjacent sequences:  A187912 A187913 A187914 * A187916 A187917 A187918 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Mar 15 2011 STATUS approved

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Last modified November 29 02:45 EST 2020. Contains 338756 sequences. (Running on oeis4.)