

A004044


Size of minimal covering code in {Z_3}^n with covering radius 1 (the next 3 terms are in the ranges 7173, 156186, 402486).


1




OFFSET

1,2


COMMENTS

Because each codeword covers 2n+1 of the 3^n words, ceiling(3^n/(2n+1)) is a lower bound.  Rob Pratt, Jan 06 2015


REFERENCES

G. D. Cohen et al., Covering Codes, NorthHolland, 1997, p. 174.


LINKS

Table of n, a(n) for n=1..5.
D. Brink, The Inverse Football Pool Problem, J. Int. Seq. 14 (2011) # 11.8.8.
H. Hamalainen et al., Football pools  a game for mathematicians, Amer. Math. Monthly, 102 (1995), 579588.
G. Keri, Tables for Bounds on Covering Codes
Index entries for sequences related to covering codes


CROSSREFS

A column of A060439.
Sequence in context: A306838 A171879 A171877 * A192152 A217098 A262314
Adjacent sequences: A004041 A004042 A004043 * A004045 A004046 A004047


KEYWORD

nonn,hard


AUTHOR

N. J. A. Sloane


EXTENSIONS

Bounds corrected and corresponding reference added by Jan Kristian Haugland, Mar 10 2010


STATUS

approved



