A079186 - OEIS

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A079186

Number of non-anti-commutative closed binary operations on a set of order n.

5

0, 0, 8, 13851, 3530555392, 266023223876953125, 9644962193498535546171949056, 246832875573638552740275218239438131202951, 6127827569844832702316847785612357470342156990019367075840, 193794664362053647720926884692597177807303542565053791345764052714030485961865

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OFFSET

0,3

LINKS

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

C. van den Bosch, Closed binary operations on small sets

Index entries for sequences related to groupoids

FORMULA

a(n) = n^(n^2) - (n^n)*((n^2-n)^((n^2-n)/2)).

a(n) = A002489(n) - A079189(n).

a(n) = Sum_{k>=1} A079178(n,k)*A079210(n,k).

PROG

(PARI) a(n) = n^(n^2) - (n^n)*((n^2-n)^((n^2-n)/2)) \\ Andrew Howroyd, Jan 23 2022

CROSSREFS

Cf. A002489, A079187 (non-isomorphic), A079188, A079189, A079210.

Sequence in context: A079235 A134373 A246959 * A247975 A198404 A079597

Adjacent sequences: A079183 A079184 A079185 * A079187 A079188 A079189

KEYWORD

nonn

AUTHOR

Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003

EXTENSIONS

a(0)=0 prepended and terms a(5) and beyond from Andrew Howroyd, Jan 23 2022

STATUS

approved