It wants the first character removed as well, if you set it to 0 it will also grab that character.

Just curious why is it 1 instead for 0? Isn't the first letter placed at 0?

Great!

Yes, i agree on this one.

Oh I see youre right! thank you for pointing that out. :)

You've misunderstood the problem slightly. It's not asking if n is a Mersenne prime, but if it produces a Mersenne prime using the provided definition (M_n = 2ⁿ - 1).

Approved

python new test framework is required. updated in this fork

basic tests could be added in full tests suite.

An Issue is for reporting that something needs to be changed about the kata itself. Use Question for questions about your own code. If you think something should change about the description then you need to elaborate - an Issue needs to be something actionable.

This is because substr prints the number of characters after the starting index. Had you started from 0, you would just need to subtract 1 to exclude the last element.
But since you have started from 1, it has shifted the range by 1, which means the last character is included again. So you need to subtract 2.

Not a kata issue! Please use question label next time~~

Note that you should optimize your code as tests can go up to 10 million (JS) && 100 million (python).