OFFSET
1,5
COMMENTS
a(n) = 10 for n > 20.
EXAMPLE
Set of non-divisors of n=12: {5,7,8,9,10,11}, therefore
a(12)=#{0,1,5,7,8,9}=6.
MATHEMATICA
Table[Length[Union[Flatten[IntegerDigits/@Complement[Range[n], Divisors[ n]]]]], {n, 80}] (* Harvey P. Dale, Jan 06 2019 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, May 28 2004
STATUS
approved