

A322654


Number of binary operations on an nset that satisfy (ab)c = (ac)b for all a,b,c.


0




OFFSET

0,3


COMMENTS

Equivalently, these are operations for which the functions induced by right multiplication commute with one another. The operations of subtraction, division, and exponentiation satisfy this identity on appropriate domains.


LINKS

Table of n, a(n) for n=0..6.
J. Benaloh and M. de Mare, OneWay Accumulators: A Decentralized Alternative to Digital Signatures, in: Tor Helleseth, Advances in Cryptology — EUROCRYPT '93, SpringerVerlag Berlin Heidelberg, 1994, 274285 (Link to PDF).


FORMULA

a(n) = Sum_{k=1..n} k!*Stirling2(n,k)*c(n,k), where c(n,k) is the number of sets of k distinct functions from {1..n} to itself that are mutually commutative.


CROSSREFS

Cf. A019538, A254570.
Sequence in context: A014382 A035308 A212925 * A323532 A273032 A185277
Adjacent sequences: A322651 A322652 A322653 * A322655 A322656 A322657


KEYWORD

nonn,more


AUTHOR

David Radcliffe, Dec 21 2018


STATUS

approved



