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A128017
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Expansion of (1+2x+x^2-x^3)/(1-x^2+x^4).
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4
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1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1, 1, 1, 2, 2, 1, 1, -1, -1, -2, -2, -1, -1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Hankel transform of A128014, A128015, A005717(n+1).
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FORMULA
| a(n)=(1-sqrt(3)/2)cos(5*pi*n/6+pi/3)-sin(5*pi*n/6+pi/3)/2+cos(pi*n/6+pi/6)/2+(1+sqrt(3)/2)sin(pi*n/6+pi/6)
a(n)=(1/12)*{-2*[(n+1) mod 12]-[(n+3) mod 12]+[(n+5) mod 12]+2*[(n+7) mod 12]+[(n+9) mod 12]-[(n+11) mod 12]}, with n>=0. - Paolo P. Lava (paoloplava(AT)gmail.com), Jun 01 2007
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CROSSREFS
| Cf. A128016.
Sequence in context: A138385 A030614 A128016 * A096285 A175078 A121561
Adjacent sequences: A128014 A128015 A128016 * A128018 A128019 A128020
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KEYWORD
| easy,sign
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Feb 11 2007
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