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A363036
Triangular array read by rows. T(n,k) is the number of regular elements in the semigroup of all binary relations on [n] that have rank k, n>=0, 0<=k<=n.
0
1, 1, 1, 1, 9, 6, 1, 49, 306, 114, 1, 225, 8550, 26376, 5256, 1, 961, 194850, 3311250, 4669200, 507720
OFFSET
0,5
LINKS
K. K.-H. Butler and G. Markowsky, The Number of Maximal Subgroups of the Semigroup of Binary Relations, Kyungpook Math. J. Vol 12, June 1972.
EXAMPLE
1;
1, 1;
1, 9, 6;
1, 49, 306, 114;
1, 225, 8550, 26376, 5256;
1, 961, 194850, 3311250, 4669200, 507720;
...
CROSSREFS
Cf. A354279 (row sums), A003425 (main diagonal), A060867 (column k=1), A354741.
Sequence in context: A220669 A064230 A286331 * A354741 A355333 A089479
KEYWORD
nonn,tabl,more
AUTHOR
Geoffrey Critzer, May 17 2023
STATUS
approved