A058167 - OEIS

A058167

Triangle read by rows: T(n,k) is the number of labeled commutative semigroups of order n with k idempotents.

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, 3287166928, 896150920, 812261856, 854806120, 707722680, 413149464, 152565280, 27019896

(list; table; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..36.

Index entries for sequences related to semigroups

EXAMPLE

Triangle begins:

4, 2;

24, 30, 9;

260, 492, 312, 76;

4805, 10060, 9900, 4900, 1065;