%I #24 Feb 24 2019 01:14:15
%S 1,2,3,8,19,57,209,884,4148,21156,115985,678581,4213609,27644450,
%T 190899336,1382958560,10480142163,82864869821,682076806177,
%U 5832742205076,51724158235392,474869816156772,4506715738447345,44152005855084369,445958869294805313,4638590332229999378
%N Rank of the inverse semigroup D_n of all difunctional relations on an n-element set.
%H James East, A. Vernitski, <a href="https://arxiv.org/abs/1612.04935">Ranks of ideals in inverse semigroups of difunctional binary relations</a>, arXiv preprint arXiv:1612.04935 [math.GR], 2016.
%F a(n) = A000110(n) + n for n >= 3 (see Theorem 2.3 of the East-Vernistki paper). - _James East_, Feb 27 2018
%Y The rightmost diagonal of A294432.
%K nonn
%O 0,2
%A _N. J. A. Sloane_, Nov 13 2017
%E More terms from _James East_, Feb 27 2018