The OEIS is supported by the many generous donors to the OEIS Foundation.


(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A001403 Number of combinatorial configurations of type (n_3). 12
0, 0, 0, 0, 0, 0, 1, 1, 3, 10, 31, 229, 2036, 21399, 245342, 3004881, 38904499, 530452205, 7640941062 (list; graph; refs; listen; history; text; internal format)
A combinatorial configuration of type (n_3) consists of an (abstract) set of n points together with a set of n triples of points, called lines, such that each point belongs to 3 lines and each line contains 3 points.
Bokowski and Sturmfels, Comput. Synthetic Geom., Lect Notes Math. 1355, p. 41.
CRC Handbook of Combinatorial Designs, 1996, p. 255.
Branko Grünbaum, Configurations of Points and Lines, Graduate Studies in Mathematics, 103 (2009), American Mathematical Society.
D. Hilbert and S. Cohn-Vossen, Geometry and the Imagination, Chelsea, NY, 1952, Ch. 3.
F. Levi, Geometrische Konfigurationen, Hirzel, Leipzig, 1929.
Pisanski, T. and Randic, M., Bridges between Geometry and Graph Theory, in Geometry at Work: Papers in Applied Geometry (Ed. C. A. Gorini), M.A.A., Washington, DC, pp. 174-194, 2000.
B. Polster, A Geometrical Picture Book, Springer, 1998, p. 28.
Sturmfels and White, Rational realizations..., in H. Crapo et al. editors, Symbolic Computation in Geometry, IMA preprint, Univ. Minn., 1988.
David Wells, Penguin Dictionary of Curious and Interesting Geometry, 1991, p. 72.
A. Betten and D. Betten, Regular linear spaces, Beiträge zur Algebra und Geometrie, 38 (1997), 111-124.
A. Betten and D. Betten, Tactical decompositions and some configurations v_4, J. Geom. 66 (1999), 27-41.
A. Betten, G. Brinkmann and T. Pisanski, Counting symmetric configurations v_3, Discrete Appl. Math., 99 (2000), 331-338.
M. Boben et al., Small triangle-free configurations of points and lines, Preprint series, Vol. 42 (2004), 938, University of Ljubljana.
M. Boben et al., Small triangle-free configurations of points and lines, Discrete Comput. Geom., 35 (2006), 405-427.
Jürgen Bokowski and Vincent Pilaud, Enumerating topological (n_k)-configurations, arXiv:1210.0306 [cs.CG], 2012.
H. Gropp, Configurations and their realization, Discr. Math. 174 (1997), 137-151.
Kaplan, Nathan; Kimport, Susie; Lawrence, Rachel; Peilen, Luke; Weinreich, Max Counting arcs in projective planes via Glynn’s algorithm. J. Geom. 108, No. 3, 1013-1029 (2017).
B. Sturmfels and N. White, All 11_3 and 12_3 configurations are rational, Aeq. Math., 39 1990 254-260.
Von Sterneck, Die Config. 11_3, Monat. f. Math. Phys., 5 325-330 1894.
Von Sterneck, Die Config. 12_3, Monat. f. Math. Phys., 6 223-255 1895.
Eric Weisstein's World of Mathematics, Configuration.
The Fano plane is the only (7_3) configuration. It contains 7 points 1,2,...,7 and 7 triples, 124, 235, 346, 457, 561, 672, 713.
The unique (8_3) configuration consists of the triples 125, 148, 167, 236, 278, 347, 358, 456.
There are three configurations (9_3), one of which arises from Pappus's theorem. See the World of Mathematics "Configuration" link above for diagrams of all three.
There are nine configurations (10_3), one of which is the familiar configuration arising from Desargues's theorem (see Loy illustration).
Cf. A023994, A099999 (geometrical configurations), A100001 (self-dual configurations), A098702, A098804, A098822, A098841, A098851, A098852, A098854.
Sequence in context: A079522 A325579 A034016 * A072136 A286444 A080406
N. J. A. Sloane, D.Glynn(AT)math.canterbury.ac.nz
Von Sterneck has 228 instead of 229. His error was corrected by Gropp. The n=15 term was computed by Dieter and Anton Betten, University of Kiel.
a(16)-a(18) from the Betten, Brinkmann and Pisanski article.
a(19) from the Pisanski et al. article.

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 23 00:10 EDT 2023. Contains 365532 sequences. (Running on oeis4.)