Question 162
Prove that for every positive integer $n$ the equation
$$
x^2 + 15y^2 = 4^n
$$
has at least $n$ non-negative integer solutions $(x, y)$.
$$
x^2 + 15y^2 = 4^n
$$
has at least $n$ non-negative integer solutions $(x, y)$.
MathNet 2010 — Part 07 Question 162
Math Olympiad Vault · MathNet 2010 — Part 07