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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
1, 3, 5, 9, 27 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

REFERENCES

G. D. Cohen et al., Covering Codes, North-Holland, 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), 579-588.

G. Keri, Tables for Bounds on Covering Codes

Index entries for sequences related to covering codes

CROSSREFS

A column of A060439.

Sequence in context: A114001 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

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Last modified February 20 09:15 EST 2019. Contains 320325 sequences. (Running on oeis4.)