I think the notes from the overtone series are physically not in tune but also you should try to bend them in tune when you do the overtone exercise...
From wikipedia :
Harmonic Note Variance
1st C1 0 cents
2nd C2 0 cents
3rd G2 +2 cents
4th C3 0 cents
5th E3 −14 cents
6th G3 +2 cents
7th Bb3 −31 cents
Harmonic Note Variance
8th C4 0 cents
9th D4 +4 cents
10th E4 −14 cents
11th G♭4 −49 cents
12th G4 +2 cents
13th Ab4 +41 cents
14th Bb4 −31 cents
Harmonic Note Variance
15th B4 −12 cents
16th C5 0 cents
17th C#5 +5 cents
18th D5 +4 cents
19th D#5 −2 cents
20th E5 −14 cents
Victor.
From wikipedia :
Harmonic Note Variance
1st C1 0 cents
2nd C2 0 cents
3rd G2 +2 cents
4th C3 0 cents
5th E3 −14 cents
6th G3 +2 cents
7th Bb3 −31 cents
Harmonic Note Variance
8th C4 0 cents
9th D4 +4 cents
10th E4 −14 cents
11th G♭4 −49 cents
12th G4 +2 cents
13th Ab4 +41 cents
14th Bb4 −31 cents
Harmonic Note Variance
15th B4 −12 cents
16th C5 0 cents
17th C#5 +5 cents
18th D5 +4 cents
19th D#5 −2 cents
20th E5 −14 cents
Victor.