A124847
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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A023531 → (1/2)D²+2D+1 → x ↦ x+1
(match reversed triangle)
1 · 3, 1 · 6, 6, 1 · 10, 18, 9, 1 … row sums 1, 4, 13, 38, 104, 272, 688, 1696, …