OFFSET
0,2
COMMENTS
Note that gcd(0,m) = m for any m.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = 4*A064608(n) + 5 for n > 0, a(0)=1. - Alois P. Heinz, Jun 03 2013
MAPLE
with(numtheory):
a:= n-> `if`(n=0, 1, 5+4*add(mobius(k)^2*floor(n/k), k=1..n)):
seq(a(n), n=0..100); # Alois P. Heinz, Jun 03 2013
MATHEMATICA
f[n_] := Length[Complement[Union[Flatten[Table[If[Abs[i]*Abs[j] ≤ n && GCD[i, j] ≤ 1, {i, j}], {i, -n, n}, {j, -n, n}], 1]], {Null}]]; Table[f[n], {n, 0, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Price, Jun 03 2013
STATUS
approved