Certainly, many researchers and mathematicians are trying to study primes over the set of natural numbers. We try to use natural numbers for indexing prime numbers. From this, the first question which arises in my mind is can we actually index primes with natural numbers and find a closed form expression for predicting the nth prime?
I believe the answer is No. The reason is, while plotting Y vs X graph, there exists a trend iff X is independent of Y. Like while doing time series analysis, your time axis is independent of parameter of Y axis. For the case of primes, I don’t think this is possible. One might prove in future that primes are the basis for the set of natural numbers, however this is beyond scope of mathematics at present, because firstly natural numbers set don’t form a vector space. Because of which some other way must be devised to prove that primes are basis for the natural numbers. If it is somehow proven, since span elements of basis form the set itself, and elements are linearly independent from each other, it becomes reasonable to argue that since primes itself form natural numbers, thus if we use natural numbers which is more or less a positional number system, can never have a closed form expression for predicting the nth prime number.
If this can be progressed further and if someone finds a new set of which primes are not basis, the set will have no linear mapping with set of natural numbers.
Any comments on the discussion are appreciable.