

A003035


Maximal number of 3tree rows in ntree orchard problem.
(Formerly M0982)


4



0, 0, 1, 1, 2, 4, 6, 7, 10, 12, 16, 19, 22, 26
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OFFSET

1,5


COMMENTS

It is known that a(15) is 31 or 32, a(16)=37 and a(17) is 40, 41 or 42.  N. J. A. Sloane, Feb 11 2013


REFERENCES

P. Brass et al., Research Problems in Discrete Geometry, Springer, 2005.
S. A. Burr, in The Mathematical Gardner, Ed. D. A. Klarner, p. 94, Wadsworth, 1981.
S. A. Burr, B. Grünbaum and N. J. A. Sloane, The Orchard Problem, Geometriae Dedicata, 2 (1974), 397424.
H. E. Dudeney, Amusements in Mathematics, Nelson, London, 1917, page 56.
M. Gardner, Time Travel and Other Mathematical Bewilderments. Freeman, NY, 1988, Chap. 22.
B. Grünbaum, Arrangements and Spreads. American Mathematical Society, Providence, RI, 1972, p. 22.
John Jackson, Rational Amusements for Winter Evenings, London, 1821.
F. Levi, Geometrische Konfigurationen, Hirzel, Leipzig, 1929.
Purdy, George B., and Justin W. Smith. "Lines, circles, planes and spheres." Discrete & Computational Geometry 44.4 (2010): 860882. [Makes use of A003035 in a formula.  N. J. A. Sloane, Oct 19 2017]
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..14.
S. A. Burr, B. Grünbaum and N. J. A. Sloane, The Orchard Problem, Geometriae Dedicata, 2 (1974), 397424.
Z. H. Du, Orchard Planting Problem [From Du, Zhao Hui, Nov 20 2008] [Seems to concentrate on the 4 trees per line version.  N. J. A. Sloane, Oct 16 2010]
Noam D. Elkies, On some pointsandlines problems and configurations, arXiv:math/0612749 [math.MG], 2006; [Concerned with other versions of the problem].
B. Green, T. Tao, On sets defining few ordinary lines, arXiv:1208.4714. (Shows that a(n) = [n(n3)/6]+1 for all sufficiently large n.)
Ed Pegg, Jr., Illustration showing that a(15) >= 31.
Ed Pegg, Jr., Illustration showing that a(15) >= 31 [Another version that uses all 31 triplets from 7 to 7 which sum to 0 (mod 15). Coordinates are: {7, {1  Sqrt[3], 1 + 2 Sqrt[3]}}, {6, {2 (2 + Sqrt[3]), 5}}, {5, {0, 3}}, {4, {2 (2 + Sqrt[3]), 1}}, {3, {2, 1}}, {2, {2, 1}}, {1, {2 (2 + Sqrt[3]), 1}}, {0, {0, 3}}, {1, {2 (2 + Sqrt[3]), 5}}, {2, {1 + Sqrt[3], 1  2 Sqrt[3]}}, {3, {2 (2 + Sqrt[3]), 1  2 Sqrt[3]}}, {4, {2  Sqrt[3], 1}}, {5, {0, 0}}, {6, {2 + Sqrt[3], 1}}, {7, {2 (2 + Sqrt[3]), 1 + 2 Sqrt[3]}}]
Ed Pegg, Jr., Illustration showing that a(15) >= 31 and a(16) >= 37
Ed Pegg, Jr., Illustration for a(16) = 37 [Based on a drawing in BurrGrünbaumSloane (1974). The bottom left point is at (sqrt(3), sqrt(5)). Note that 3 points and one line are at infinity.]
Ed Pegg, Jr., Illustrations of constructions for 9 through 28 trees.
G. B. Purdy and J. W. Smith, Lines, circles, planes and spheres, Discrete Comput. Geom., 44 (2010), 860882.
N. J. A. Sloane, Illustration of initial terms (from GrünbaumBurrSloane paper)
Eric Weisstein's World of Mathematics, OrchardPlanting Problem.


CROSSREFS

Cf. A006065, A008997, A058212.
Sequence in context: A198033 A071260 A026407 * A094453 A191200 A026398
Adjacent sequences: A003032 A003033 A003034 * A003036 A003037 A003038


KEYWORD

nonn,nice,hard,more,changed


AUTHOR

N. J. A. Sloane.


EXTENSIONS

13 and 14 trees result from Du, Zhao Hui, Nov 20 2008


STATUS

approved



