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A258720 Number of non-self-dual groupoids which are equal to their duals. 9
0, 3, 1596, 89460896, 1241763541901150, 7162795001623210170643008, 25488450150907291894372809845206177481, 77841043345568973636021232493841647618443964915982324, 270925719901279918478856582434909122129159229348142178651137261056627814 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
T. Tamura, Some contributions of computation to semigroups and groupoids, pp. 229-261 of J. Leech, editor, Computational Problems in Abstract Algebra. Pergamon, Oxford, 1970. (Annotated and scanned copy)
FORMULA
a(n) = (A001329(n) - A029850(n))/2. - Andrew Howroyd, May 06 2023
CROSSREFS
Sequence in context: A246637 A302132 A346653 * A262652 A262500 A290944
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 18 2015
EXTENSIONS
Terms a(5) and beyond from Andrew Howroyd, May 06 2023
STATUS
approved

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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)