I have to translate some mathematic exercises into English, can you help by correct my versions?

I don't know which should be choosen?

1.How many natural numbers are there in the interval [1;1000] such that the fraction (n^2 +4 +23)/n+4 is not in the lowest terms?
2.How many natural numbers in the interval [1;1000] such that fraction (n^2+23)/n+4 is not in the lowest term ?
3.How many natural numbers are there lying in the interval [1;1000] such that fraction.....is not in the lowest term?

If they are all grammatical, which is the best ? which sounds mathematical? which is not grammatical?