A181415 -id:A181415 - cp's OEIS frontend

A181512 Irregular triangle a(n,k) = A181415(n,k) / A036040(n,k).

1, 1, 1, 1, 2, 2, 1, 3, 3, 6, 6, 1, 4, 4, 12, 12, 24, 24, 1, 5, 5, 5, 20, 20, 20, 60, 60, 120, 120, 1, 6, 6, 6, 30, 30, 30, 30, 120, 120, 120, 360, 360, 720, 720, 1, 7, 7, 7, 7, 42, 42, 42, 42, 42, 210, 210

Offset: 1

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Alford Arnold, Oct 26 2010

nonn
tabf

This is an irregular table related to labeled rooted trees and to Bell numbers.

A181511 contains the same values, without repetition.

			1;
1,1;
1,2,2;
1,3,3,6,6;
1,4,4,12,12,24,24;
1,5,5,5,20,20,20,60,60,120,120;
1,6,6,6,30,30,30,30,120,120,120,360,360,720,720;

Cf. A181511, A181513 (row sums).

sum_{k=1.. A000041(n)} a(n,k) = A181513(n). (Row sums)

cp's OEIS Frontend

A181512 Irregular triangle a(n,k) = A181415(n,k) / A036040(n,k).

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