Find all integers n > l such that 1″ + 2 +…+(n − 1)” is divisible by n.​

1 thought on “Find all integers n > l such that 1″ + 2 +…+(n − 1)” is divisible by n.​”

1. Step-by-step explanation:

   n2+1n+1 is a natural number

   ⇔n2+2n+1−2nn+1 is a natural number

   ⇔(n+1)2−2nn+1 is a natural number

   ⇔n+1−2n+2−2n+1 is a natural number

   ⇔n+1−2−2n+1 is a natural number

   ⇔(n+1)|2

   ⇔n=1 because n must be a positive odd number and 2 is divisible by (n+1).

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