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I added a value to B2 so delete or comment that line out. The results of Debug.Print will show in the Immediate window of the Visual Basic Editor (VBE).
Sub Calculatex()
Dim Lengths() As Variant
Dim a As Double
Range("B2").Value = 4
a = Range("B2").Value
Lengths() = Ram(a)
Debug.Print Lengths(1)
Range("B21:D21").Value = Lengths()
End Sub
Function Ram(a As Double) As Variant
Dim Tap() As Variant
Dim b As Double
Dim c As Double
b = a + 1
c = b + 1
Tap() = Array(a, b, c)
Ram = Tap()
End Function