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A079171
Number of isomorphism classes of closed binary operations (groupoids) on a set of order n, listed by class size.
20
1, 4, 6, 3, 12, 78, 3237, 2, 1, 14, 30, 275, 495, 48810, 178932325
OFFSET
1,2
COMMENTS
Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!)
A002489(n) is equal to the sum of the products of each element in row n of this sequence and the corresponding element of A079210.
The sum of each row n is given by A001329(n).
EXAMPLE
First four rows:
1;
4, 6;
3, 12, 78, 3237;
2, 1, 14, 30, 275, 495, 48810, 178932325.
CROSSREFS
Cf. A002489, A001329. a(n, A027423(n)) = A030245(n).
Sequence in context: A082193 A255767 A274926 * A029678 A123732 A244339
KEYWORD
nonn,tabf
AUTHOR
Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003
STATUS
approved