[correct_horse]

I think you meant to say length of string, length of string / 2, length of string / 3, ...

https://en.wikipedia.org/wiki/Harmonic

[adw]

Indeed I did! Thank you. (This is what happens when you write in a hurry.)

[mkagenius]

Hope you had a nice flight. Happy new year.

[adw]

One leg down, the long one to go...