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A168058 Expansion of x + sqrt(1-2x-3x^2). 2
1, 0, -2, -2, -4, -8, -18, -42, -102, -254, -646, -1670, -4376, -11596, -31022, -83670, -227268, -621144, -1706934, -4713558, -13072764, -36398568, -101704038, -285095118, -801526446, -2259520830, -6385455594, -18086805002 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n+2) = -2*A001006(n). Hankel transform is (-1)^n*A168057(n).

Essentially the same as A167022. - R. J. Mathar, Nov 18 2009

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

FORMULA

a(n) = 0^n - 2*Sum_{k=0..floor((n-2)/2)} C(n-2,2k)*A000108(k).

EXAMPLE

1 - 2*x^2 - 2*x^3 - 4*x^4 - 8*x^5 - 18*x^6 - 42*x^7 - 102*x^8 - 254*x^9 - ...

MATHEMATICA

CoefficientList[Series[x + Sqrt[1 - 2 x - 3 x^2], {x, 0, 50}], x] (* G. C. Greubel, Jul 08 2016 *)

CROSSREFS

Cf. A168055.

Sequence in context: A063402 A175195 A139800 * A007971 A126068 A167022

Adjacent sequences:  A168055 A168056 A168057 * A168059 A168060 A168061

KEYWORD

easy,sign

AUTHOR

Paul Barry, Nov 17 2009

STATUS

approved

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Last modified February 23 08:36 EST 2019. Contains 320420 sequences. (Running on oeis4.)