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

1,5

Comments

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

A181511 contains the same values, without repetition.

Links

Table of n, a(n) for n=1..56.

Formula

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

Example

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;

Crossrefs

Cf. A181511, A181513 (row sums).

Sequence in context: A109380 A167754 A011020 * A076019 A071453 A212306

Adjacent sequences: A181509 A181510 A181511 * A181513 A181514 A181515

Keyword

nonn,tabf

Author

Alford Arnold, Oct 26 2010

Status

approved