



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
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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



