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A058167 Triangle: Labeled commutative semigroups of order n with k idempotents. 0
1, 4, 2, 24, 30, 9, 260, 492, 312, 76, 4805, 10060, 9900, 4900, 1065, 157956, 284130, 348420, 259500, 112500, 22566, 12277440, 11892846, 14768775, 14093380, 9063600, 3592554, 674611 (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; 4,2; 24,30,9; 260,492,312,76; 4805,10060,9900,4900,1065; ...

CROSSREFS

Row sums give A023815. Main diagonal: A058164(n+1).

Sequence in context: A134461 A298593 A228474 * A140331 A095896 A286798

Adjacent sequences:  A058164 A058165 A058166 * A058168 A058169 A058170

KEYWORD

nonn,tabl,hard

AUTHOR

Christian G. Bower, Nov 15 2000

STATUS

approved

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Last modified October 20 21:49 EDT 2018. Contains 316404 sequences. (Running on oeis4.)