Root regions
Nodes grouped by the interval that contains every root of every row (proved, for all n). A node can have several proved regions; the sharpest is the smallest interval.
Nodes with all roots in (-1, 0) (6)
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A225472: Triangle read by rows, k!*S_3(n, k) where S_m(n, k) are the Stirling-Frobenius subset numbers of order m; n >= 0, k >= 0.
1 · 2, 3 · 4, 21, 18 · 8, 117, 270, 162 … row sums 1, 5, 43, 557, 9643, 208685, 5419243, …
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A134991: Triangle of Ward numbers T(n,k) read by rows.
1 · 1, 3 · 1, 10, 15 · 1, 25, 105, 105 … row sums 1, 4, 26, 236, 2752, 39208, 660032, …
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A063007: T(n,k) = binomial(n,k)*binomial(n+k,k), 0 <= k <= n, triangle read by rows.
1 · 1, 2 · 1, 6, 6 · 1, 12, 30, 20 … row sums 1, 3, 13, 63, 321, 1683, 8989, 48639, …
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A033282: Triangle read by rows: T(n, k) is the number of diagonal dissections of a convex n-gon into k+1 regions.
1 · 1, 2 · 1, 5, 5 · 1, 9, 21, 14 … row sums 1, 3, 11, 45, 197, 903, 4279, 20793, …
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A019538: Triangle of numbers T(n,k) = k!*Stirling2(n,k) read by rows (n >= 1, 1 <= k <= n).
1 · 1, 2 · 1, 6, 6 · 1, 14, 36, 24 … row sums 1, 3, 13, 75, 541, 4683, 47293, 545835, …
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A225473: Triangle read by rows, k!*S_4(n, k) where S_m(n, k) are the Stirling-Frobenius subset numbers of order m; n >= 0, k >= 0.
1 · 3, 4 · 9, 40, 32 · 27, 316, 672, 384 … row sums 1, 7, 81, 1399, 32289, 931687, …