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A131429
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Triangle read by rows: T(n,k) = C(n) + C(k) - 1 where C(n) = A000108(n) are the Catalan numbers, 0 <= k <= n.
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4
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1, 1, 1, 2, 2, 3, 5, 5, 6, 9, 14, 14, 15, 18, 27, 42, 42, 43, 46, 55, 83, 132, 132, 133, 136, 145, 173, 263, 429, 429, 430, 433, 442, 470, 560, 857, 1430, 1430, 1431, 1434, 1443, 1471, 1561, 1858, 2859, 4862, 4862, 4863, 4866, 4875, 4903, 4993, 5290, 6291, 9723
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OFFSET
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0,4
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COMMENTS
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Left column = Catalan numbers, A000108. Right border = 2*A000108 - 1. Row sums = A131430: (1, 2, 7, 25, 88, 311, 1114, ...).
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LINKS
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FORMULA
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EXAMPLE
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First few rows of the triangle are:
1;
1, 1;
2, 2, 3;
5, 5, 6, 9;
14, 14, 15, 18, 27;
42, 42, 43, 46, 55, 83;
...
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PROG
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(PARI) T(n, k)=if(k<=n, binomial(2*n, n)/(n+1) + binomial(2*k, k)/(k+1) - 1, 0) \\ Andrew Howroyd, Sep 01 2018
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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