For which nnn is x2−y2=nx^2 - y^2 = nx2−y2=n guaranteed to have at least one integer solution?
n≡2(mod4)n \equiv 2 \pmod 4n≡2(mod4)
n≡1(mod4)n \equiv 1 \pmod 4n≡1(mod4)
n≡0(mod2)n \equiv 0 \pmod 2n≡0(mod2)
n≡3(mod4)n \equiv 3 \pmod 4n≡3(mod4)