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%I #18 Jan 01 2020 12:04:39
%S 1,1,1,2,7,31,184,1351,12524,146468,2177570,41374407,1008220289,
%T 31559446774,1269310589336,65562045668340,4345161435996517
%N Number of isomorphism classes of irreducible posets with n labeled points.
%H G. Brinkmann, B. D. McKay, <a href="http://dx.doi.org/10.1023/A:1016543307592">Posets on up to 16 Points</a>, Order 19 (2) (2002) 147-179 (Table 1).
%H J. A. Wright, <a href="https://www.ams.org/journals/notices/197006/197006FullIssue.pdf">There are 718 6-point topologies, quasi-orderings and transgraphs</a>, Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.
%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 G.f.: A(x) = 2-1/B(x), where B(x) is g.f. of A000112. - _Vladeta Jovovic_, Jan 15 2006
%t A000112 = Cases[Import["https://oeis.org/A000112/b000112.txt", "Table"], {_, _}][[All, 2]];
%t B[x_] = A000112.x^Range[0, Length[A000112] - 1];
%t A[x_] = 2 - 1/B[x];
%t CoefficientList[A[x] + O[x]^Length[A000112], x] (* _Jean-François Alcover_, Jan 01 2020 *)
%Y Cf. A046908.
%K nonn,more
%O 0,4
%A John A. Wright.
%E More terms from _Vladeta Jovovic_, Jan 15 2006