A001470
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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A118931: Triangle, read by rows, where T(n,k) = n!/(k!*(n-3*k)!*3^k) for n>=3*k>=0.
(match row sums)
1 · 1 · 1 · 1, 2 … row sums 1, 1, 1, 3, 9, 21, 81, 351, …