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A038020 Triangle: T(n,k), k<=n: groupoids with a nontrivial symmetry with n elements and k idempotents. 0
0, 0, 0, 2, 0, 2, 9, 54, 0, 30, 15376, 12664, 14304, 4096, 3187 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..14.

Index entries for sequences related to groupoids

FORMULA

Difference of A038018 and A038019.

CROSSREFS

Cf. A001329, A030248, A030251, A030271.

Sequence in context: A091518 A096734 A220234 * A211910 A250406 A107094

Adjacent sequences:  A038017 A038018 A038019 * A038021 A038022 A038023

KEYWORD

nonn,tabl

AUTHOR

Christian G. Bower, May 15 1998

STATUS

approved

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Last modified June 25 20:02 EDT 2022. Contains 354851 sequences. (Running on oeis4.)