A026945
identification: the entry's rule defines the sequence for every index; tail: the sequence is the entry's tail after some prefix rows; match_*: finite agreement only.
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A280580: Triangle read by rows: T(n,k) = binomial(2*n,2*k)*binomial(2*n-2*k,n-k)/(n+1-k) for 0<=k<=n.
(match row sums)
1 · 1, 1 · 2, 6, 1 · 5, 30, 15, 1 … row sums 1, 2, 9, 51, 323, 2188, 15511, 113634, …