"From the properties of Pell's equation, we know that there are infinite sets of solutions... So this is a positive odd number divisible by 3... From the characteristic equation, we know the corresponding recursion formula..."

At the desk, he pushed his glasses that had slipped off his nose with his ring finger and fluently wrote a series of equations on the manuscript paper to the person next to him, "Therefore, the condition is only met when X?=27. At this time, n