Ответ:

  1. \(n\in\{-2,-1,0,1,2,\ldots\}\).
  2. \(n\in\{1,2,3,\ldots\}\).
  3. \(n\in\{2,3,4,\ldots\}\).
  4. \(n\in\{-4,-3,-2,-1,0,1,\ldots\}\).