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A294431
Rank of the inverse semigroup D_n of all difunctional relations on an n-element set.
1
1, 2, 3, 8, 19, 57, 209, 884, 4148, 21156, 115985, 678581, 4213609, 27644450, 190899336, 1382958560, 10480142163, 82864869821, 682076806177, 5832742205076, 51724158235392, 474869816156772, 4506715738447345, 44152005855084369, 445958869294805313, 4638590332229999378
OFFSET
0,2
LINKS
James East, A. Vernitski, Ranks of ideals in inverse semigroups of difunctional binary relations, arXiv preprint arXiv:1612.04935 [math.GR], 2016.
FORMULA
a(n) = A000110(n) + n for n >= 3 (see Theorem 2.3 of the East-Vernistki paper). - James East, Feb 27 2018
CROSSREFS
The rightmost diagonal of A294432.
Sequence in context: A148041 A148042 A077269 * A148043 A321255 A243791
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 13 2017
EXTENSIONS
More terms from James East, Feb 27 2018
STATUS
approved