OFFSET
0,4
COMMENTS
If it is possible to make every value from 1 to n using at most 2 of the coins used in a country, what is the minimum possible value of the sum of the coins in this country?
By considering sets {1, 2, ..., r, 2r, 3r, ..., (s-1)r}, it is conjectured that the asymptotic behavior is a(n) ~ 3/4 * 2^(1/3) * n^(4/3).
LINKS
EXAMPLE
a(8) = 8: {1,3,4}
MATHEMATICA
a[n_] := Min[Total /@ Select[Subsets[Range[n], Floor[(n + 1)/2]], Complement[Range[n], Total /@ Join[Subsets[ #, {1, 2}], Transpose[{#, #}]]] == {} &]]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
David Bevan, Sep 29 2009
STATUS
approved