%I #31 Jul 10 2022 14:58:10
%S 1,1,0,0,24,1080,52440,3281880,277953144,32418855000,5239070305080,
%T 1173944480658840,363936227764858584,155521768202208047640,
%U 91218870039317505477720,73113879800794757415243480,79743817918540500914682249144,117883366412734188786535902826200,235329353612778837110901775412557560
%N Number of connected irreducible posets with n labeled points.
%D J. A. Wright, There are 718 6-point topologies, quasi-orderings and transgraphs, Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.
%H S. R. Finch, <a href="http://www.people.fas.harvard.edu/~sfinch/">Series-parallel networks</a>
%H S. R. Finch, <a href="/A000084/a000084_2.pdf">Series-parallel networks</a>, July 7, 2003. [Cached copy, with permission of the author]
%H J. A. Wright, <a href="/A000798/a000798_4.pdf">Letter to N. J. A. Sloane, Apr 06 1972, listing 18 sequences</a>
%H <a href="/index/Pos#posets">Index entries for sequences related to posets</a>
%F From _Geoffrey Critzer_, Jul 09 2022: (Start)
%F E.g.f.: 1 + log(A(x)) - A(x)(1-1/A(x))^2 where A(x) is the e.g.f. for A001035.
%F a(n) = A001927(n) - Sum_{k>=2} A354615(n,k). (End)
%t nn = 18; A[x_] := Total[Cases[Import["https://oeis.org/A001035/b001035.txt",
%t "Table"], {_, _}][[All, 2]]*Table[x^(i - 1)/(i - 1)!, {i, 1, 19}]];
%t Range[0, nn]! CoefficientList[ Series[(1 + Log[A[x]]) - A[ x] (1 - 1/A[x])^2 , {x, 0, nn}], x] (* _Geoffrey Critzer_, Jul 09 2022 *)
%Y A003431 gives isomorphism classes of these posets.
%K nonn
%O 0,5
%A John A. Wright.
%E a(8)-a(18) from _Geoffrey Critzer_, Jul 09 2022
%E a(0) changed to 1 by _Geoffrey Critzer_, Jul 10 2022