Let n and k be positive integers with k ≤ n. From an n × n array of dots, a k × k array of dots is selected.The figure above shows two examples where the selected k × k array is enclosed in a square. How many pairs (n, k) are possible so that exactly 48 of the dots in the n × n array are NOT in the selected k × k array?
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真尼玛不应该,最后竟然数漏了一个K=1.。。。。。!!!!!
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