A046907 -id:A046907 - cp's OEIS frontend

A046908 Number of irreducible posets with n labeled points.

1, 1, 1, 7, 97, 2251, 80821, 4305127, 332273257, 36630174931, 5711638291981, 1249898984911567, 381230073532620577, 161042140788424003291, 93667063572594041040421, 74610767840852891620692727, 80997478506602342803118178457, 119313601058907927882431190269731, 237541348427311374857037021264415741

Offset: 0

John A. Wright

nonn

J. A. Wright, There are 718 6-point topologies, quasi-orderings and transgraphs, Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.

G. Brinkmann, B. D. McKay, Posets on up to 16 Points, Order 19 (2) (2002) 147-179 (Table III, up to 18 points)
J. A. Wright, Letter to N. J. A. Sloane, Apr 06 1972, listing 18 sequences
Index entries for sequences related to posets

Cf. A046907.

A001035 = Cases[Import["https://oeis.org/A001035/b001035.txt", "Table"], {, }][[All, 2]]; lg = Length[A001035];
B[x_] = Sum[A001035[[n + 1]] x^n/n!, {n, 0, lg - 1}];
A[x_] = 2 - 1/B[x];
CoefficientList[A[x] + O[x]^lg, x]*Range[0, lg - 1]! (* Jean-François Alcover, Jan 01 2020 *)

E.g.f.: A(x) = 2-1/B(x), where B(x) is e.g.f. of A001035. - Vladeta Jovovic, Jan 10 2006

More terms from Vladeta Jovovic, Jan 10 2006

a(16)-a(18) from A001035 by Jean-François Alcover, Jan 01 2020

cp's OEIS Frontend

A046908 Number of irreducible posets with n labeled points.

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