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A219731
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Irregular triangle M_2(n,k) read by rows: number of maximum k-matchings in rooted plane trees of size n, 1<=k<=n/2, 2<=n.
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0
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1, 4, 9, 3, 16, 28, 25, 135, 15, 36, 462, 220, 49, 1274, 1638, 91, 64, 3024, 8400, 1820, 81, 6426, 33660, 18360, 612, 100, 12540, 112860, 125970, 15504, 121, 22869, 330330, 665665, 197505, 4389, 144, 39468, 868296, 2900898, 1700160, 134596, 169, 65065, 2091375, 10883600, 11182600, 2072070, 32890
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OFFSET
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2,2
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LINKS
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FORMULA
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M(n,k) = sum_{l=max(n-2k,1) .. n-k} binomial(l,n-2*k)*binomial(2*n-3*k-l-1,n-k-l)*binomial(3*k+l-2,l-1)/l.
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EXAMPLE
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1;
4;
9,3;
16,28;
25,135,15;
36,462,220;
49,1274,1638,91;
64,3024,8400,1820;
81,6426,33660,18360,612;
100,12540,112860,125970,15504;
121,22869,330330,665665,197505,4389;
144,39468,868296,2900898,1700160,134596;
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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