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A038023 Triangle: T(n,k), k<=n: commutative groupoids with a nontrivial symmetry with n elements and k idempotents. 2
0, 0, 0, 0, 0, 0, 3, 6, 0, 4, 96, 214, 128, 64, 38, 54248, 83925, 54223, 28254, 10223, 1894 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,7

LINKS

Table of n, a(n) for n=0..20.

Index entries for sequences related to groupoids

FORMULA

Difference of A038021 and A038022.

CROSSREFS

Cf. A001329, A001425, A030259, A030262, A030265.

Sequence in context: A178567 A182196 A278488 * A008954 A169890 A181907

Adjacent sequences:  A038020 A038021 A038022 * A038024 A038025 A038026

KEYWORD

nonn,tabl,more

AUTHOR

Christian G. Bower, May 15 1998

STATUS

approved

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Last modified October 21 16:25 EDT 2019. Contains 328302 sequences. (Running on oeis4.)