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A221173 a(0)=-3, a(1)=4; thereafter a(n) = 2*a(n-1) + a(n-2). 5
-3, 4, 5, 14, 33, 80, 193, 466, 1125, 2716, 6557, 15830, 38217, 92264, 222745, 537754, 1298253, 3134260, 7566773, 18267806, 44102385, 106472576, 257047537, 620567650, 1498182837, 3616933324, 8732049485, 21081032294, 50894114073, 122869260440, 296632634953 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..1000

José L. Ramírez, Gustavo N. Rubiano, and Rodrigo de Castro, A Generalization of the Fibonacci Word Fractal and the Fibonacci Snowflake, arXiv preprint arXiv:1212.1368, 2012

Index entries for linear recurrences with constant coefficients, signature (2,1).

FORMULA

a(n) = (1/4)*(7*sqrt(2)*((1+sqrt(2))^n-(1-sqrt(2))^n)-6*((1+sqrt(2))^n+(1-sqrt(2))^n)). - Paolo P. Lava, Jan 04 2013

a(n) = 10*A000129(n)-3*A000129(n+1). - R. J. Mathar, Jan 14 2013

G.f.: -(10*x-3) / (x^2+2*x-1). - Colin Barker, Jul 10 2015

PROG

(Haskell)

a221173 n = a221173_list !! n

a221173_list = -3 : 4 : zipWith (+)

                        (map (* 2) $ tail a221173_list) a221173_list

-- Reinhard Zumkeller, Jan 04 2013

(PARI) Vec(-(10*x-3)/(x^2+2*x-1) + O(x^100)) \\ Colin Barker, Jul 10 2015

CROSSREFS

Cf. A000129, A078343, A221172, A221174, A221175.

Sequence in context: A211518 A049895 A226117 * A051530 A240670 A048040

Adjacent sequences:  A221170 A221171 A221172 * A221174 A221175 A221176

KEYWORD

sign,easy

AUTHOR

N. J. A. Sloane, Jan 04 2013

STATUS

approved

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Last modified March 18 22:11 EDT 2019. Contains 321305 sequences. (Running on oeis4.)