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A122876
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a(0)=1, a(1)=1, a(2)=2, a(n)=a(n-1)-a(n-2) for n>2.
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2
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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; internal format)
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OFFSET
| 0,3
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COMMENTS
| Essentially the same as A057079, A087204 and A100051.
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (1,-1).
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FORMULA
| a(n)=Sum_{k, 0<=k<=[n/2]}(-2)^k*A055830(n-k,k) . G.f.:(1+2*x^2)/(1-x+x^2)
a(n)=(1/2)*[(1/2)-(1/2)*I*sqrt(3)]^(n-1)+(1/2)*[(1/2)+(1/2)*I*sqrt(3)]^(n-1)+(1/2)*I*[(1/2)-(1/2)*I *sqrt(3)]^(n-1)*sqrt(3)-(1/2)*I*[(1/2)+(1/2)*I*sqrt(3)]^(n-1)*sqrt(3)+[C(2*n,n) mod 2], with n>=0 and I=sqrt(-1) [From Paolo P. Lava (paoloplava(AT)gmail.com), Nov 19 2008]
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CROSSREFS
| Sequence in context: A131713 A099837 A100051 * A100063 A057079 A132419
Adjacent sequences: A122873 A122874 A122875 * A122877 A122878 A122879
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KEYWORD
| sign,easy
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AUTHOR
| Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Oct 24 2006
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