A221175 a(0)=-5, a(1)=6; thereafter a(n) = 2*a(n-1) + a(n-2).

-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

Offset: 0

Author

N. J. A. Sloane, Jan 04 2013

Keywords

• sign
• easy

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 [cs.DM], 2012-2014.
• Index entries for linear recurrences with constant coefficients, signature (2,1).

Crossrefs

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

Programs

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

Formula

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