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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..25.

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

Adjacent sequences:  A294428 A294429 A294430 * A294432 A294433 A294434

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Nov 13 2017

EXTENSIONS

More terms from James East, Feb 27 2018

STATUS

approved

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Last modified July 13 13:48 EDT 2020. Contains 335688 sequences. (Running on oeis4.)