A006246 - OEIS

A006246

Number of simple arrangements of pseudolines in the projective plane with an oriented marked cell; number of oriented abstract order types of n points (distinguishing mirror-symmetric copies)
(Formerly M0920)

1, 1, 1, 2, 3, 20, 242, 6405, 316835, 28627261, 4686329954

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OFFSET

1,4

COMMENTS

Previous name was: Number of primitive sorting networks on n elements.

REFERENCES

M. H. Klin et al., "2D-configurations and clique-cyclic orientations of the graphs L(K_p)", pages 149-162 of Reports in Molecular Theory, Vol. 1, 1990.

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=1..11.

D. E. Knuth, Axioms and Hulls, Lect. Notes Comp. Sci., Vol. 606, Springer-Verlag, Berlin, Heidelberg, 1992, p.35, entry C_n.

John Mackey and Bernardo Subercaseaux, Pentagon Minimization without Computation, arXiv:2409.17098 [math.CO], 2024. See p. 4.

Index entries for sequences related to sorting

CROSSREFS

Cf. A006245. See A006247 for abstract order types when mirror-symmetric copies are identified.

Sequence in context: A353921 A361028 A177946 * A349600 A110372 A292866

Adjacent sequences: A006243 A006244 A006245 * A006247 A006248 A006249

KEYWORD

nonn,more,changed

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Definition corrected by Günter Rote, Dec 02 2021

STATUS

approved