A128019 - OEIS

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A128019

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

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; internal format)

	OFFSET	`0,2`
	COMMENTS	`Binomial transform is A128018.`
	FORMULA	`a(n)=3^floor((n+1)/2)*(-1)^C(n+1,2);`
	CROSSREFS	`Cf. A108411.` `Sequence in context: A147510 A146474 A145957 * A108411 A056449 A162436` `Adjacent sequences: A128016 A128017 A128018 * A128020 A128021 A128022`
	KEYWORD	`easy,sign`
	AUTHOR	`Paul Barry (pbarry(AT)wit.ie), Feb 11 2007`

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Last modified February 17 06:27 EST 2012. Contains 205998 sequences.