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Search: id:A128615
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| A128615 |
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Expansion of x/(1+x+x^2-x^3-x^4-x^5). |
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+0
1
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| 0, 1, -1, 0, 2, -2, 0, 3, -3, 0, 4, -4, 0, 5, -5, 0, 6, -6, 0, 7, -7, 0, 8, -8, 0, 9, -9, 0, 10, -10, 0, 11, -11, 0, 12, -12, 0, 13, -13, 0, 14, -14, 0, 15, -15, 0, 16, -16, 0, 17, -17, 0, 18, -18, 0, 19, -19
(list; graph; listen)
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OFFSET
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0,5
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COMMENT
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Partial sums are 0,1,0,0,2,0,0,3,0,0,4,...
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FORMULA
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G.f.: x/((1-x)(1+x+x^2)^2)=x(1-x)/(1-x^3)^2; a(n)=-cos(2*pi*n/3)/9+(2*sqrt(3)*n/9+1/sqrt(3))*sin(2*pi*n/3)+1/9;
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CROSSREFS
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Cf. A087508.
Sequence in context: A129236 A127465 A127899 this_sequence A087508 A095731 A048142
Adjacent sequences: A128612 A128613 A128614 this_sequence A128616 A128617 A128618
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KEYWORD
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easy,sign
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Mar 13 2007
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