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A063024
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Reversion of y - y^2 - y^3 - y^4 - y^5.
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0
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0, 1, 1, 3, 11, 45, 196, 894, 4215, 20377, 100463, 503191, 2553291, 13097469, 67808104, 353851124, 1859313324, 9828998946, 52237988523, 278952216129, 1495976545546, 8053571710250, 43507491045810, 235784617161780
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OFFSET
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0,4
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LINKS
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FORMULA
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a(n)=sum(k=1..n-1, (sum(j=0..k, binomial(k,j)*sum(i=j..n-k+j-1, binomial(j,i-j)*binomial(k-j,n-3*(k-j)-i-1))))*binomial(n+k-1,n-1)/n, n>1. a(1)=1. [Vladimir Kruchinin, May 10 2011]
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MATHEMATICA
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CoefficientList[InverseSeries[Series[y - y^2 - y^3 - y^4 - y^5, {y, 0, 30}], x], x]
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PROG
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(Maxima)
a(n):=if n<2 then n else sum((sum(binomial(k, j)*sum(binomial(j, i-j)*binomial(k-j, n-3*(k-j)-i-1), i, j, n-k+j-1), j, 0, k))*binomial(n+k-1, n-1), k, 1, n-1)/n; /* Vladimir Kruchinin, May 10 2011 */
(PARI)
x='x+O('x^66);
gf=serreverse(x-sum(j=2, 6, x^j));
Vec(gf)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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