How many ways can n+1 distinguishable objects be placed into n indistinguishable boxes, so that no box is empty?

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I've been having a really hard time coming up with a closed form formula for this. Solutions online all use Stirling numbers which my course has not covered. Right now what I have is [((n-1)^n) - ((n-2)^n) -... ((n-k)^n) ]/(n-1)! tbh I dont know if it is even right

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The only thing you have to choose are the two items that share a box. Once you have that, you have to put one item in every other box and you don't care which box each one goes in.