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A135440 a(n) = a(n-1) + 2a(n-2). 6
-1, 4, 2, 10, 14, 34, 62, 130, 254, 514, 1022, 2050, 4094, 8194, 16382, 32770, 65534, 131074, 262142, 524290, 1048574, 2097154, 4194302, 8388610, 16777214, 33554434, 67108862, 134217730, 268435454, 536870914, 1073741822, 2147483650, 4294967294, 8589934594, 17179869182, 34359738370 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

First differences of A014551. - Reinhard Zumkeller, Jan 02 2013

LINKS

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

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

FORMULA

From R. J. Mathar, Feb 19 2008: (Start)

O.g.f.: -1/(2*x-1) - 2/(1+x).

a(n) = 2^n - 2*(-1)^n. (End)

a(n) = 2*A014551(n-1), n>0. - Paul Curtz, Jun 01 2011

E.g.f.: exp(2*x) - 2*exp(-x). - G. C. Greubel, Oct 14 2016

MATHEMATICA

f[n_]:=2/(n+1); x=4; Table[x=f[x]; Numerator[x], {n, 0, 5!}] (* Vladimir Joseph Stephan Orlovsky, Mar 12 2010 *)

LinearRecurrence[{1, 2}, {-1, 4}, 25] (* or *) Table[2^n - 2*(-1)^n, {n, 0, 25}] (* G. C. Greubel, Oct 14 2016 *)

PROG

(Haskell)

a135440 n = a135440_list !! n

a135440_list = zipWith (-) (tail a014551_list) a014551_list

-- Reinhard Zumkeller, Jan 02 2013

CROSSREFS

Sequence in context: A075086 A284782 A128781 * A215500 A188128 A336914

Adjacent sequences:  A135437 A135438 A135439 * A135441 A135442 A135443

KEYWORD

sign,easy

AUTHOR

Paul Curtz, Feb 18 2008

EXTENSIONS

More terms from R. J. Mathar, Feb 19 2008

STATUS

approved

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Last modified July 24 04:25 EDT 2021. Contains 346273 sequences. (Running on oeis4.)