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Search: id:A085403
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| A085403 |
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Expansion of (1-x+sqrt(1-6x+x^2))/2 in powers of x. |
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+0
8
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| 1, -2, -2, -6, -22, -90, -394, -1806, -8558, -41586, -206098, -1037718, -5293446, -27297738, -142078746, -745387038, -3937603038, -20927156706, -111818026018, -600318853926, -3236724317174, -17518619320890, -95149655201962, -518431875418926, -2832923350929742
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OFFSET
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0,2
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COMMENT
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Series reversion of x(Sum_{k>=0} a(k)x^k) is x(Sum_{k>=0} A027307(k)x^k).
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FORMULA
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G.f.: (1-x+sqrt(1-6x+x^2))/2. (=1/g.f. A006318)
Given g.f. A(x), y=A(x)x satisfies 0=f(x, y) where f(x, y)=y(y-x)+(x+y)x^2 . - Michael Somos May 23 2005 */
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PROGRAM
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(PARI) a(n)=polcoeff((1-x+sqrt(1-6*x+x^2+x*O(x^n)))/2, n)
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CROSSREFS
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A minor variation of A006318. a(n)=-A006318(n-1), n>1.
Sequence in context: A004077 A007985 A097090 this_sequence A112478 A138801 A069466
Adjacent sequences: A085400 A085401 A085402 this_sequence A085404 A085405 A085406
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KEYWORD
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sign
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AUTHOR
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Michael Somos, Jun 28 2003
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