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A116088
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Riordan array (1, x*(1+x)^2).
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4
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1, 0, 1, 0, 2, 1, 0, 1, 4, 1, 0, 0, 6, 6, 1, 0, 0, 4, 15, 8, 1, 0, 0, 1, 20, 28, 10, 1, 0, 0, 0, 15, 56, 45, 12, 1, 0, 0, 0, 6, 70, 120, 66, 14, 1, 0, 0, 0, 1, 56, 210, 220, 91, 16, 1, 0, 0, 0, 0, 28, 252, 495, 364, 120, 18, 1
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OFFSET
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0,5
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LINKS
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FORMULA
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G.f.: 1/(1-x*y*(1+x)^2).
Number triangle T(n,k) = C(2*k, n-k) = C(n,k)*C(3*k,n)/C(3*k,k).
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EXAMPLE
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Triangle begins as:
1;
0, 1;
0, 2, 1;
0, 1, 4, 1;
0, 0, 6, 6, 1;
0, 0, 4, 15, 8, 1;
0, 0, 1, 20, 28, 10, 1;
0, 0, 0, 15, 56, 45, 12, 1;
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MATHEMATICA
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Flatten[Table[Binomial[2k, n-k], {n, 0, 20}, {k, 0, n}]] (* Harvey P. Dale, Oct 22 2012 *)
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PROG
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(PARI) {T(n, k) = binomial(2*k, n-k)}; \\ G. C. Greubel, May 09 2019
(Magma) [[Binomial(2*k, n-k): k in [0..n]]: n in [0..10]]; // G. C. Greubel, May 09 2019
(Sage) [[binomial(2*k, n-k) for k in (0..n)] for n in (0..10)] # G. C. Greubel, May 09 2019
(GAP) Flat(List([0..10], n->List([0..n], k-> Binomial(2*k, n-k) ))); # G. C. Greubel, May 09 2019
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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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