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%I #16 Jan 01 2020 10:29:50
%S 1,1,1,7,97,2251,80821,4305127,332273257,36630174931,5711638291981,
%T 1249898984911567,381230073532620577,161042140788424003291,
%U 93667063572594041040421,74610767840852891620692727,80997478506602342803118178457,119313601058907927882431190269731,237541348427311374857037021264415741
%N Number of 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 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 III, up to 18 points)
%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 E.g.f.: A(x) = 2-1/B(x), where B(x) is e.g.f. of A001035. - _Vladeta Jovovic_, Jan 10 2006
%t A001035 = Cases[Import["https://oeis.org/A001035/b001035.txt", "Table"], {_, _}][[All, 2]]; lg = Length[A001035];
%t B[x_] = Sum[A001035[[n + 1]] x^n/n!, {n, 0, lg - 1}];
%t A[x_] = 2 - 1/B[x];
%t CoefficientList[A[x] + O[x]^lg, x]*Range[0, lg - 1]! (* _Jean-François Alcover_, Jan 01 2020 *)
%Y Cf. A046907.
%K nonn
%O 0,4
%A John A. Wright.
%E More terms from _Vladeta Jovovic_, Jan 10 2006
%E a(16)-a(18) from A001035 by _Jean-François Alcover_, Jan 01 2020
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