Prime numbers

Does anyone else find the Sieve of Eratosthenes and the ilk a totally pointless concept?

It like over optimising a Java program that could be written in C in a short space of time.

>>26>>>f(4)
3>>>f(4)
9>>>f(4)
1

There you have it, a nondeterministic function.
Also, while you are speaking like a retard that doesn't know what words mean, hopefully on purpose, you should note that you can indeed do what you vaguely appear to be unintelligibly talking about, i.e. calculating the xth digit without first calculating the previous x - 1 digits, for π's binary representation.