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A058168 Triangle: Number of asymmetric commutative semigroups of order n with k idempotents. 1
1, 2, 1, 3, 5, 1, 7, 18, 12, 2, 24, 65, 73, 34, 5, 133, 276, 399, 309, 123, 18, 1722, 1595, 2240, 2331, 1500, 544, 81 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..28.

Index entries for sequences related to semigroups

EXAMPLE

1; 2,1; 3,5,1; 7,18,12,2; 24,65,73,34,5; ...

CROSSREFS

Row sums give A058105.

Sequence in context: A059234 A120852 A285490 * A058169 A178074 A002249

Adjacent sequences:  A058165 A058166 A058167 * A058169 A058170 A058171

KEYWORD

nonn,tabl,hard

AUTHOR

Christian G. Bower, Nov 19 2000

STATUS

approved

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Last modified October 22 06:02 EDT 2018. Contains 316432 sequences. (Running on oeis4.)