good!

That is correct. This solution functions correctly only because of the constraints specified. If the initial value is 10 then no matter what I do, my opponent can force me to lose the game, so I know that I will never recieve 10 as an input.

@SnickersTheCat, you are right, but the description specifies but you have a friend in judging who has excluded all hopeless initial l values for you, so a losing value will not be tested.

does this return 0 as a value which would be out of range?

when I pass 10 as length it is retuurning 0 which I would think would be outside of the allowed test values

In case of INT/INT division - fractional part is being truncated.

How can the solution be just that lol

It's about the diagonals (complete ones and partials ones). A very good explanation was made by benjaminzwhite in his python solution of the kata, I can't do better. ;)

Sorry for the question, but I can't understand the 2a(a-1)(3b-a-1)/3 and the corrispective 2b(b-1)(3a-b-1)/3.
I want an explanation, please.

Duplicate of https://www.codewars.com/kata/55905b7597175ffc1a00005a ? (Just a difference of performance?)

Same idea with mine.

Thank you for this! I altered it from recurrence_rate to recurrence but missed that spot.
corrected

Solution corrected thanks for picking this up

the function name in the initial code is recurrence_rate but the tests expect it to be named recurrence

Yeah seems... I didn't solve the kata but in set up the function name is recurrence_rate, which is I guess incorrect... Can someone who solved the kata confirm?