How many ways can three of the letters in the word 'KANATA' be arranged?

The total number of three letter combinations is supposed to be 34, but I don't understand how to calculate this number.

I thought that it would be 6!/(3!x(6-3)!) = 20 since there are six letters to choose from, but we are limited to choosing only 3 letters and also 3 letters repeat.

Can someone explain to me the logic to solve this?