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 A175882 Number of groupoids of order n with no identity element. 1
 1, 0, 12, 19440, 4293918720, 298022460937500000, 10314424627908807366593740800, 256923577502496762167593902921782457650400, 6277101735385253516143083463326608130132905949327651766272, 196627050475552807506414708879663572595247698231546775823411085055396409324160 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Andrew Howroyd, Table of n, a(n) for n = 0..20 ProofWiki, Count of Binary Operations Without Identity FORMULA a(n) = n^(n^2) - n^(((n-1)^2)+1) = A002489(n) - A090602(n). PROG (PARI) a(n) = n^(n^2) - n^(((n-1)^2)+1) \\ Andrew Howroyd, Jan 23 2022 CROSSREFS Cf. A002489, A090602. Sequence in context: A125547 A159421 A159369 * A216874 A012736 A013750 Adjacent sequences: A175879 A175880 A175881 * A175883 A175884 A175885 KEYWORD nonn AUTHOR Matt Westwood, Dec 05 2010 EXTENSIONS a(0)=1 prepended and terms a(7) and beyond from Andrew Howroyd, Jan 23 2022 STATUS approved

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Last modified July 20 20:43 EDT 2024. Contains 374459 sequences. (Running on oeis4.)