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Number of unlabeled disconnected posets with n elements.
0

%I #20 Jul 18 2022 13:13:41

%S 0,0,1,2,6,19,80,395,2487,19890,206565,2804453,49872647,1158843214,

%T 35049606566,1374685228988,69690886873398,4554367168841547

%N Number of unlabeled disconnected posets with n elements.

%H Gunnar Brinkmann and Brendan D. McKay, <a href="http://users.cecs.anu.edu.au/~bdm/papers/posets.pdf">Posets on up to 16 points</a>.

%H Salah Uddin Mohammad, Md. Shah Noor, and Md. Rashed Talukder, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL25/Uddin/uddin6.html">An Exact Enumeration of the Unlabeled Disconnected Posets</a>, J. Int. Seq., Vol. 25 (2022), Article 22.5.4.

%F a(n) = A000112(n) - A000608(n).

%Y Cf. A000112, A000608, A342500.

%K nonn,more

%O 0,4

%A _Salah Uddin Mohammad_, Nov 15 2021