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A122434

Expansion of (1+x)^3/(1+x+x^2).

1, 2, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0, -1, 1, 0

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OFFSET

0,2

COMMENTS

Row sums of number triangle A122433. Binomial transform is A077859.

LINKS

Table of n, a(n) for n=0..68.

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

FORMULA

a(n) = 2*sqrt(3)*cos(2*Pi*n/3+Pi/6)/3+C(1,n)+C(0,n).

a(n) = -A049347(n) if n>=2 . - R. J. Mathar, Feb 08 2008

MATHEMATICA

CoefficientList[Series[(1+x)^3/(1+x+x^2), {x, 0, 70}], x] (* or *) PadRight[ {1, 2, 0}, 71, {-1, 1, 0}] (* Harvey P. Dale, Apr 25 2012 *)

CROSSREFS

Sequence in context: A362221 A260728 A065339 * A141571 A164067 A353918

Adjacent sequences: A122431 A122432 A122433 * A122435 A122436 A122437

KEYWORD

easy,sign

AUTHOR

Paul Barry, Sep 04 2006

STATUS

approved