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A221175 a(0)=-5, a(1)=6; thereafter a(n) = 2*a(n-1) + a(n-2). 5
-5, 6, 7, 20, 47, 114, 275, 664, 1603, 3870, 9343, 22556, 54455, 131466, 317387, 766240, 1849867, 4465974, 10781815, 26029604, 62841023, 151711650, 366264323, 884240296, 2134744915, 5153730126, 12442205167, 30038140460, 72518486087, 175075112634 (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)*(11*sqrt(2)*((1+sqrt(2))^n-(1-sqrt(2))^n)-10*((1+sqrt(2))^n+(1-sqrt(2))^n)). - Paolo P. Lava, Jan 04 2013

a(n) = 16*A000129(n)-5*A000129(n+1). - R. J. Mathar, Jan 14 2013

G.f.: -(16*x-5) / (x^2+2*x-1). - Colin Barker, Jul 10 2015

PROG

(Haskell)

a221175 n = a221175_list !! n

a221175_list = -5 : 6 : zipWith (+)

                        (map (* 2) $ tail a221175_list) a221175_list

-- Reinhard Zumkeller, Jan 04 2013

(PARI) Vec(-(16*x-5)/(x^2+2*x-1) + O(x^50)) \\ Colin Barker, Jul 10 2015

CROSSREFS

Cf. A000129, A078343, A221172, A221173, A221174.

Sequence in context: A111018 A161925 A078694 * A048007 A273402 A217295

Adjacent sequences:  A221172 A221173 A221174 * A221176 A221177 A221178

KEYWORD

sign,easy

AUTHOR

N. J. A. Sloane, Jan 04 2013

STATUS

approved

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Last modified February 16 20:45 EST 2019. Contains 320189 sequences. (Running on oeis4.)