Fixed

Not an issue

Your solution may be off-by-one. Or the kata might be, I'm really not sure anymore.

Interesting... Which language are you using?

@mattbrendzel, @nbeck the problem lies with the parentheses on the class name Sudoku() and passing self as parameter to the method. Try removing these. Also, write an initialize method.

Same here, have you find something ?

Yes, you are right. I'll modify the description. The algorithm must be greedy: at each stage one must find the biggest square that can be used in the sum of squares.
For example if n=11, n^2=121 and at least I have two decompositions: [1 2 4 10] and [2 6 9]. I keep [1 2 4 10] because 10^2 is bigger than 9^2 to remove from 121.
For the decomposition of 50^2, I have the solution [1,3,5,8,49] which is "greedy" because 49^2 is bigger to remove from 50^2 than 48^2 or worse 40^2.
Hopefully it would be more precise. Thanks for the help.