A122876 - OEIS

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A122876

a(0)=1, a(1)=1, a(2)=2, a(n)=a(n-1)-a(n-2) for n>2.

1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1, 1, 2, 1, -1, -2, -1 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`0,3`
	COMMENTS	`Essentially the same as A057079, A087204 and A100051.`
	LINKS	`Table of n, a(n) for n=0..78.` `Index to sequences with linear recurrences with constant coefficients, signature (1,-1).`
	FORMULA	`a(n)=Sum_{k, 0<=k<=[n/2]}(-2)^kA055830(n-k,k) . G.f.:(1+2x^2)/(1-x+x^2)` `a(n)=(1/2)[(1/2)-(1/2)Isqrt(3)]^(n-1)+(1/2)[(1/2)+(1/2)Isqrt(3)]^(n-1)+(1/2)I[(1/2)-(1/2)I sqrt(3)]^(n-1)sqrt(3)-(1/2)I[(1/2)+(1/2)Isqrt(3)]^(n-1)sqrt(3)+[C(2*n,n) mod 2], with n>=0 and I=sqrt(-1) [From Paolo P. Lava, Nov 19 2008]`
	CROSSREFS	`Sequence in context: A131713 A099837 A100051 * A100063 A057079 A132419` `Adjacent sequences: A122873 A122874 A122875 * A122877 A122878 A122879`
	KEYWORD	`sign,easy`
	AUTHOR	`Philippe DELEHAM, Oct 24 2006`
	STATUS	`approved`

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Last modified May 19 01:49 EDT 2013. Contains 225428 sequences.