%I #36 Sep 14 2019 06:39:09
%S 0,0,0,0,0,0,0,0,0,1,2,3,3,6,9,11
%N a(n) is the least number of empty convex pentagons ("convex 5-holes") spanned by a set of n points in the Euclidean plane in general position (i.e., no three points on a line).
%C The value a(10) = 1 was determined by Harborth, who also constructed a set of 9 points without convex 5-holes. The values a(11) = 2 and a(13) = 3 were determined by Dehnhardt. Aichholzer found point sets showing that a(14) <= 6 and a(15) <= 9, and the exact values a(13) = 3, a(14) = 6, and a(15) = 9 were determined in the Bachelor's thesis of Scheucher, supervised by Aichholzer and Hackl.
%C The value a(16) = 11 was determined using a ILP/SAT solver. For more information check out the link below with title "On 5-Holes". - _Manfred Scheucher_, Aug 18 2018
%D K. Dehnhardt, Leere konvexe Vielecke in ebenen Punktmengen, PhD thesis, TU Braunschweig, Germany, 1987, in German.
%H O. Aichholzer, M. Balko, T. Hackl, J. Kynčl, I. Parada, M. Scheucher, P. Valtr, and B. Vogtenhuber, <a href="http://arxiv.org/abs/1703.05253">A superlinear lower bound on the number of 5-holes</a>, arXiv:1703.05253 [math.CO], 2017.
%H O. Aichholzer, R. Fabila-Monroy, T. Hackl, C. Huemer, A. Pilz, and B. Vogtenhuber, <a href="http://dx.doi.org/10.1016/j.comgeo.2013.12.002">Lower bounds for the number of small convex k-holes</a>, Computational Geometry: Theory and Applications, 47(5):605-613, 2014.
%H EuroGIGA - CRP ComPoSe, <a href="http://www.eurogiga-compose.eu/posezo/n13_c1_min_convex_3_4_5_holes/n13_c1_min_convex_3_4_5_holes.php">A set of 13 points with 3 convex 5-holes</a>
%H EuroGIGA - CRP ComPoSe, <a href="http://www.eurogiga-compose.eu/posezo/n14_c1_6_convex_5_holes/n14_c1_6_convex_5_holes.php">A set of 14 points with 6 convex 5-holes</a>
%H EuroGIGA - CRP ComPoSe, <a href="http://www.eurogiga-compose.eu/posezo/n15_c1_9_convex_5_holes/n15_c1_9_convex_5_holes.php">A set of 15 points with 9 convex 5-holes</a>
%H EuroGIGA - CRP ComPoSe, <a href="http://www.eurogiga-compose.eu/posezo/n16_c1_11_convex_5_holes/n16_c1_11_convex_5_holes.php">A set of 16 points with 11 convex 5-holes</a>
%H H. Harborth, <a href="http://dx.doi.org/10.5169/seals-32945">Konvexe Fünfecke in ebenen Punktmengen</a>, Elemente der Mathematik, 33:116-118, 1978, in German.
%H M. Scheucher, <a href="http://www.ist.tugraz.at/staff/scheucher/publ/bachelors_thesis_2013.pdf">Counting Convex 5-Holes</a>, Bachelor's thesis, Graz University of Technology, Austria, 2013, in German.
%H M. Scheucher, <a href="http://www.ist.tugraz.at/scheucher/5holes/">On 5-Holes</a>.
%F From _Manfred Scheucher_, Mar 22 2017: (Start)
%F a(n) = Omega(n log^(4/5)(n)) and a(n) = O(n^2).
%F Conjecture: a(n) = Theta(n^2). (End)
%Y Cf. A063541 and A063542 for convex 3- and 4-holes, respectively.
%Y Cf. A006247 and A063666 for equivalence classes (w.r.t. orientation triples) of point sets in the plane.
%K nonn,more
%O 1,11
%A _Manfred Scheucher_, Aug 18 2016
%E a(16) from _Manfred Scheucher_, Mar 22 2017