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A004044 Size of minimal covering code in {Z_3}^n with covering radius 1 (the next 3 terms are in the ranges 71-73, 156-186, 402-486). 1

%I

%S 1,3,5,9,27

%N Size of minimal covering code in {Z_3}^n with covering radius 1 (the next 3 terms are in the ranges 71-73, 156-186, 402-486).

%C Because each codeword covers 2n+1 of the 3^n words, ceil(3^n/(2n+1)) is a lower bound. - _Rob Pratt_, Jan 06 2015

%D G. D. Cohen et al., Covering Codes, North-Holland, 1997, p. 174.

%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 H. Hamalainen et al., <a href="http://www.jstor.org/stable/2974552">Football pools - a game for mathematicians</a>, Amer. Math. Monthly, 102 (1995), 579-588.

%H G. Keri, <a href="http://www.sztaki.hu/~keri/codes">Tables for Bounds on Covering Codes</a>

%H <a href="/index/Coa#covcod">Index entries for sequences related to covering codes</a>

%Y A column of A060439.

%K nonn,hard

%O 1,2

%A _N. J. A. Sloane_.

%E Bounds corrected and corresponding reference added by _Jan Kristian Haugland_, Mar 10 2010

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Last modified March 24 06:56 EDT 2019. Contains 321444 sequences. (Running on oeis4.)