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A003431 Number of connected irreducible posets with n labeled points.
(Formerly M4857)
4
0, 1, 0, 0, 1, 12, 104, 956, 10037, 126578, 1971005, 38569954, 958347642, 30400603560, 1234260982770, 64187360439352, 4275470549123119 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=0..16.

S. R. Finch, Series-parallel networks

S. R. Finch, Series-parallel networks, July 7, 2003. [Cached copy, with permission of the author]

R. P. Stanley, Enumeration of posets generated by disjoint unions and ordinal sums, Proc. Amer. Math. Soc. 45 (1974), 295-299.

R. P. Stanley, Letter to N. J. A. Sloane, c. 1991

J. A. Wright, Letter to N. J. A. Sloane, Apr 06 1972, listing 18 sequences

Index entries for sequences related to posets

CROSSREFS

Cf. A003430, A046906.

Sequence in context: A024454 A222540 A279301 * A173835 A334168 A220111

Adjacent sequences:  A003428 A003429 A003430 * A003432 A003433 A003434

KEYWORD

nonn,nice,more

AUTHOR

N. J. A. Sloane and Richard Stanley

EXTENSIONS

More terms from Richard Stanley, Jun 19 2003

2 more terms from Vladeta Jovovic, Feb 17 2008

STATUS

approved

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Last modified March 8 20:52 EST 2021. Contains 341953 sequences. (Running on oeis4.)