MathDB
Games in Quarantine

Source: 2020 Taiwan TST Round 2 Mock Exam 4

May 2, 2020
algebrapolynomialTaiwan

Problem Statement

Alice and Bob are stuck in quarantine, so they decide to play a game. Bob will write down a polynomial f(x)f(x) with the following properties:
(a) for any integer nn, f(n)f(n) is an integer; (b) the degree of f(x)f(x) is less than 187187.
Alice knows that f(x)f(x) satisfies (a) and (b), but she does not know f(x)f(x). In every turn, Alice picks a number kk from the set {1,2,,187}\{1,2,\ldots,187\}, and Bob will tell Alice the value of f(k)f(k). Find the smallest positive integer NN so that Alice always knows for sure the parity of f(0)f(0) within NN turns.
Proposed by YaWNeeT