A hint would be nice. I managed to calculate the number of fields but the number of moves grows astronomically so its hard to see any pettern.

Thank you for quick response! Now I understand

Before that part of the text:

...If there are multiple solutions (and there will be), return as far as possible the result with the largest possible values:...

You need to take the solution with largest possible value for numbers with multiple possibilities

Now, back to what you asked

decompose(11) must return [1,2,4,10]. Note that there are actually two ways to decompose 11², 11² = 121 = 1 + 4 + 16 + 100 = 1² + 2² + 4² + 10² but don't return [2,6,9], since 9 is smaller than 10.

Since [1,2,4,10] has 10 which is bigger than all of the numbers in [2,6,9], you should return [1,2,4,10] instead.

what's wrong with 9 being smaller than 10 if 10 is not even part of the returned sequence?

"but don't return [2,6,9], since 9 is smaller than 10."

Arigato, sensei.

'onone' should equal 'on_one'

"onone" is not the input there, it's your incorrect returned value. The input was "OnOne".

There is no mention of "onone" should equal to "on_one" in the description or examples, and the description says "accepts Pascal Case as input" how is "onone" a Pascal Case?