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%I #26 Sep 27 2020 14:48:59
%S 2,3,5,8,12,18,29,44,68
%N Number of n-dimensional 2 X 2 X ... X 2 grid graphs needed to cover an n-dimensional 3 X 3 X ... X 3 torus.
%D Patric R. J. Östergård and T. Riihonen, A covering problem for tori, Annals of Combinatorics, 7 (2003), 1-7.
%H D. Brink, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL14/Brink/brink3.html">The Inverse Football Pool Problem</a>, J. Int. Seq. 14 (2011) # 11.8.8.
%H Emil Kolev, <a href="http://www.moi.math.bas.bg/acct2014/a33.pdf">Covering of {F_3}^n with spheres of maximal radius</a>, Fourteenth International Workshop on Algebraic and Combinatorial Coding Theory, September 7-13, 2014, Svetlogorsk (Kaliningrad region), Russia pp. 198-203.
%H E. Kolev and T. Baicheva, <a href="http://www.moi.math.bas.bg/oc2013/a21.pdf">About the inverse football pool problem for 9 games</a>, Seventh International Workshop on Optimal Codes and Related Topics, September 6-12, 2013, Albena, Bulgaria pp. 125-133.
%H Patric R. J. Östergård, <a href="https://users.aalto.fi/~pat/">Home page</a>
%e Known bounds for n=10 through 13, from Kolev (2014):
%e 10 102-104
%e 11 153-172
%e 12 230-264
%e 13 345-408
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Jul 28 2003
%E I have added two terms (29 and 44). The ranges for the next terms are [66,68] and [99,104]. _David Brink_, Jun 03 2009
%E For a(9) = 68 and further bounds see Kolev and Baicheva. - _N. J. A. Sloane_, Mar 10 2014
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