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Poznate stvari | Well known stuff #4

Koliko postoji prirodnih brojeva k \geq 2 takvih da je za sve prirodne brojeve 1 \leq n < k broj n^2 - n + k prost?
Find the number of positive integers k \geq 2 such that for all positive integers 1 \leq n < k number n^2 - n + k is prime.