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A128019 Expansion of (1-3x)/(1+3x^2). 4
1, -3, -3, 9, 9, -27, -27, 81, 81, -243, -243, 729, 729, -2187, -2187, 6561, 6561, -19683, -19683, 59049, 59049, -177147, -177147, 531441, 531441, -1594323, -1594323, 4782969, 4782969, -14348907, -14348907, 43046721 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Binomial transform is A128018.

LINKS

Table of n, a(n) for n=0..31.

Index entries for linear recurrences with constant coefficients, signature (0,-3)

FORMULA

a(n)=3^floor((n+1)/2)*(-1)^C(n+1,2);

CROSSREFS

Cf. A108411.

Sequence in context: A146474 A145957 A214439 * A108411 A056449 A287479

Adjacent sequences:  A128016 A128017 A128018 * A128020 A128021 A128022

KEYWORD

easy,sign

AUTHOR

Paul Barry, Feb 11 2007

STATUS

approved

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Last modified May 28 21:37 EDT 2020. Contains 334690 sequences. (Running on oeis4.)