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A063033
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Reversion of y - y^2 + y^4.
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0
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0, 1, 1, 2, 4, 8, 14, 16, -21, -242, -1166, -4472, -15132, -46508, -130016, -323000, -660535, -786714, 1789952, 18546464, 93845290, 380532240, 1355983860, 4363436280, 12688926510, 32530717752, 67666586472, 76255301640, -240266135872
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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LINKS
| Index entries for reversions of series
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FORMULA
| a(n)=sum(j=0..(n-1)/2, (-1)^j*binomial(n-2*j-1,j)*binomial(2*n-2*j-2,n-1))/n, a(0)=0. [From Vladimir Kruchinin, Oct 11 2011]
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MATHEMATICA
| CoefficientList[InverseSeries[Series[y - y^2 + y^4, {y, 0, 30}], x], x]
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PROG
| (Maxima)
a(n):=sum((-1)^j*binomial(n-2*j-1, j)*binomial(2*n-2*j-2, n-1), j, 0, (n-1)/2)/n; [From Vladimir Kruchinin, Oct 11 2011]
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CROSSREFS
| Sequence in context: A174540 A076380 A049133 * A128309 A074202 A086303
Adjacent sequences: A063030 A063031 A063032 * A063034 A063035 A063036
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KEYWORD
| sign,easy
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AUTHOR
| Olivier Gerard (olivier.gerard(AT)gmail.com), Jul 05 2001.
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