What is the smallest prime factor of , where ?
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Given that n is even, let's define k = 2 n . We can use difference of squares to get ( 1 9 k − 8 k ) ( 1 9 k + 8 k ) . We can assume WLOG that k = 1 . Thus, we achieve ( 1 1 ) ( 2 7 ) , the smallest prime factor of which is simply 3 .