

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
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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, Seriesparallel networks
R. P. Stanley, Enumeration of posets generated by disjoint unions and ordinal sums, Proc. Amer. Math. Soc. 45 (1974), 295299.
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 A220111 A094530
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



