A049020
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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A049020: Triangle of numbers a(n,k), 0 <= k <= n: number of set partitions of {1,2,...,n} in which exactly k of the blocks have been distinguished.
(identification, match triangle)
A023531 → basis A0490201 · 1, 1 · 2, 3, 1 · 5, 10, 6, 1 … row sums 1, 2, 6, 22, 94, 454, 2430, 14214, …
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A023531 → basis A049020 → reverse
(match reversed triangle)
1 · 1, 1 · 1, 3, 2 · 1, 6, 10, 5 … row sums 1, 2, 6, 22, 94, 454, 2430, 14214, …