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A132428
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Central terms of triangle A132427.
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1
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1, 1, 3, 10, 43, 216, 1241, 7988, 56763, 440254, 3693728, 33281359, 320112326, 3270177860, 35329070470, 402128329243, 4806784533967, 60166803598106, 786622663286330, 10717555856584617, 151864784070048105
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n)=sum(k=1..n, sum(i=k..n, binomial(i-1,k-1)*binomial(i,n-i))*a(k-1)), n>0,a(0)=1. [Vladimir Kruchinin, May 02 2012]
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PROG
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(PARI) {a(n)=local(G=1+x+x*O(x^n)); for(i=0, n, G=1+x*subst(G, x, x/(1-x)^2)/(1-x)); polcoeff(subst((G-1)/x, x, x/(1+x))/(1+x), n)}
(Maxima) a(n):=if n=0 then 1 else sum(sum(binomial(i-1, k-1)*binomial(i, n-i), i, k, n)*a(k-1), k, 1, n); [Vladimir Kruchinin, May 02 2012]
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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