It's stated in the description to return undefined when the array has less than 3 elements.

can you be more specific?

hi. I gave a standard mathematical definition of an arithmetic progression and was referring to the mathemtical difference by a constant quantity (in this case you're right, the quantity is 0). I see how the word 'differs' can be misleading, so I changed the kata description(just the defintiion of the arithm seq bit) to make it more clear.

thanks for pointing that out!

Hi, can you give further explanations on your solution?

I'm having the same issue.

I passed NaN as a string as suggested too.