[Digressions] Shapes your booty, Fractales et consorts...

Sub Test1()
Application.ScreenUpdating = False
Cells.ClearContents
Calc_Spiral "J19", 1, 240, 1, 2, True, True
Columns("A:K").Delete Shift:=xlToLeft
End Sub
Sub Calc_Spiral(strStartingCell$, iStartingNumber%, iMaxCount%, iStep%, iStartingDirection%, bClockwise As Boolean, bSecond As Boolean)
Rem https://ask.libreoffice.org/t/how-to-program-draw-a-square-spiral/29883
Rem <strStartingCell> : A single cell address, e.g. "H12" representing the center of the spiral.
Rem <iStartingNumber> : Integer to be displayed inside the starting cell; Incremented by 1 for each following cell.
Rem <iMaxCount> : The total amount of cells to be drawn in the spiral;
Rem NB. Cells that fall outside of the Sheet''s edges are not counted in the total amount.
Rem <iStep> : Integer increase of the armlength after each turn in the spiral.
Rem <iStartingDirection> : Determines the direction of the second cell to be drawn, relative to the starting cell.
Rem 0=RIGHT ; 1=UP ; 2=LEFT ; 3=DOWN.
Rem <bClockwise> : Boolean indicating whether the spiral goes clockwise ( <True> ) or counter-clockwise ( <False> ).
Rem <bSecond> : If <True> , the armlength increases only every second turn instead of every turn.
Rem Example call : Calc_Spiral( "H12", 1, 100, 1, 2, True, True )
'On Error Resume Next
Dim oSheet As Worksheet, oCell As Range, iColumn%, iRow%, m%, iCount%, iDirection%, iCurrentStep%, iCurrentPos%, iArmCount%
Set oSheet = ActiveSheet
Set oCell = oSheet.Range(strStartingCell)
iRow = oCell.Row
iColumn = oCell.Column
iCount = 0
iDirection = iStartingDirection
iCurrentStep = iStep
iCurrentPos = 0
' If iCurrentStep = 0 Then iCurrentStep = 1 '
m = 1
If bClockwise Then m = 3
Do While iCount < iMaxCount
oCell.Value = iStartingNumber + iCount 'REM Display the index number inside the cell.
If iCurrentPos = iCurrentStep Then 'Rem End of Arm reached:
iArmCount = iArmCount + 1
iDirection = (iDirection + m) Mod 4 'REM Compute the Next direction.
iCurrentPos = 0
If Not bSecond Or (iCount > 0 And iArmCount Mod 2 = 0) Then iCurrentStep = iCurrentStep + iStep
End If
Select Case iDirection
Case 0 'REM Right
iColumn = iColumn + 1
Case 1 'REM Up
iRow = iRow - 1
Case 2 'REM Left
iColumn = iColumn - 1
Case 3 'REM Down
iRow = iRow + 1
End Select
Set oCell = Cells(iColumn, iRow) 'REM Go towards the Next Cell.
iCurrentPos = iCurrentPos + 1
iCount = iCount + 1
Loop
End Sub

Sub OCEBO()
mGRILLE
mPAVAGE
End Sub
Private Sub mGRILLE()
Application.ScreenUpdating = False
With Range("A1:IV256")
    .RowHeight = 4
    .ColumnWidth = 0.4
End With
Call mCouleurs
End Sub
Private Sub mPAVAGE()
Dim t(1 To 256, 1 To 256), v_PI, v_PHI, x%, y%
v_PI = 4 * Atn(1)
v_PHI = (1 + Sqr(5)) / 2
Application.ScreenUpdating = False
    For x = 1 To 256
        For y = 1 To 256
        t(x, y) = _
                    Cos((x Xor y) * v_PI * v_PHI / 23) Xor Sin(Sqr(v_PHI))
        Next
    Next
Cells(1).Resize(UBound(t, 1), UBound(t, 2)).Value = t
End Sub
Private Sub mCouleurs()
Dim mfc
mfc = Array(Array(1, 8109667), Array(5, 8711167), Array(2, 7039480))
With Range("A1:IV256")
    .FormatConditions.AddColorScale ColorScaleType:=3
    .FormatConditions(Selection.FormatConditions.Count).SetFirstPriority
    .FormatConditions(1).ColorScaleCriteria(2).Value = 50
    For k = 0 To 2
        .FormatConditions(1).ColorScaleCriteria(k + 1).Type = mfc(k)(0)
        .FormatConditions(1).ColorScaleCriteria(k + 1).FormatColor.Color = mfc(k)(1)
    Next
End With
End Sub