Question 132
Let $n \geq 1$ be a natural number. Find all positive integer solutions to the equation
$$
7 \cdot 4^{n}=a^{2}+b^{2}+c^{2}+d^{2}
$$
$$
7 \cdot 4^{n}=a^{2}+b^{2}+c^{2}+d^{2}
$$
MathNet 2005 — Part 02 Question 132
Math Olympiad Vault · MathNet 2005 — Part 02