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A190315
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Central coefficients of the Riordan matrix ((1-x-x^2)/(1-2x-x^2),(x-x^2-x^3)/(1-2x-x^2)) (A190215).
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2
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1, 2, 9, 48, 265, 1500, 8638, 50360, 296325, 1756160, 10467556, 62683896, 376838098, 2272896626, 13747543035, 83354081728, 506467851061, 3083121435312, 18799746616104, 114804614071760, 702016963933404, 4297947201746176, 26342178216979384
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = T(2*n,n), where T(n,k)=A190215(n,k).
a(n) = Sum_{i=0..n} binomial(n+i,n)*Sum_{j=0..n-i} binomial(i+j-1,j)*binomial(j,n-i-j).
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MATHEMATICA
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Table[Sum[Binomial[n+i, n]Sum[Binomial[i+j-1, j]Binomial[j, n-i-j], {j, 0, n-i}], {i, 0, n}], {n, 0, 22}]
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PROG
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(Maxima) makelist(sum(binomial(n+i, n)*sum(binomial(i+j-1, j)*binomial(j, n-i-j), j, 0, n-i), i, 0, n), n, 0, 22);
(PARI) for(n=0, 30, print1(sum(k=0, n, binomial(n+k, n)*sum(j=0, n-k, binomial(k+j-1, j)*binomial(j, n-k-j))), ", ")) \\ G. C. Greubel, Mar 04 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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