Declare @t Table(F1 Int)
Insert @t Select 1
Union all Select 2
Union all Select 3
Union all Select 5
Union all Select 6
Union all Select 8
Union all Select 9
Union all Select 10
Union all Select 12
Union all Select 13
Union all Select 14
Union all Select 15
Union all Select 20
Union all Select 21
Union all Select 22
Union all Select 23
Union all Select 100
Union all Select 101
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Select * From (
Select * From @t A
Where F1>1 And Not Exists
(Select 1 From @t Where F1=A.F1-1)
Union all
Select * From @t A
Where F1>1 And Not Exists
(Select 1 From @t Where F1=A.F1+1)) A
Order By F1