How to code a formation of objects for a RTS simulation game?

Hi, I'm trying to make a pyramid formation which look like this for my RTS game

I have already done it by doing it manually via code, but doing so can only be done using an array that have a maximum container of 9 Objects.

What I'm aiming is if I add more and more object the pyramid will become longer and taller using the for method.

For Example:

If I have 16 Game Objects it will be like this

                      1
                    4 x 2
                  8 6 3 5 7
             15 13 11 9 10 12 14

And if I have 25 Game Objects it will be like this

                      1
                    4 x 2
                  8 6 3 5 7
             15 13 11 9 10 12 14
          24 22 20 18 16 17 19 21 23

Keep in mind that x is an origin point of the formation a.k.a the first object of the array / list for Ex: Unit[0]

Here's my manually done code for the pyramid formation. As you can see it is only limited till 8 objects, but I want it to be unlimited

 for(int i = 0; i < selectedUnits.Count; i++)
 {
     ObjectStat selected0;
     selected0 = selectedUnits[0].GetComponent<ObjectStat>();
 
     if(i != 0)
     {
         ObjectStat selected = selectedUnits[i].GetComponent<ObjectStat>();
         if(i == 1)
         {
             selected.marker2DIn3DVersion.position = new 
             Vector2(selected0.marker2DIn3DVersion.position.x, 
             selected0.marker2DIn3DVersion.position.y + Range[i - 1]);
             selected.marker3D.position = new Vector2(selected0.marker3D.position.x, 
             selected0.marker3D.position.y + Range[i - 1]);
         }
         else if(i == 2)
         {
             selected.marker2DIn3DVersion.position = new 
             Vector2(selected0.marker2DIn3DVersion.position.x + Range[i - 1], 
             selected0.marker2DIn3DVersion.position.y);
             selected.marker3D.position = new Vector2(selected0.marker3D.position.x + Range
             [i - 1], 
             selected0.marker3D.position.y);
         }
         else if(i == 3)
         {
             selected.marker2DIn3DVersion.position = new 
             Vector2(selected0.marker2DIn3DVersion.position.x, 
             selected0.marker2DIn3DVersion.position.y - Range[i - 1]);
             selected.marker3D.position = new Vector2(selected0.marker3D.position.x, 
             selected0.marker3D.position.y - Range[i - 1]);
         }
         else if(i == 4)
         {
             selected.marker2DIn3DVersion.position = new 
             Vector2(selected0.marker2DIn3DVersion.position.x - Range[i - 1], 
             selected0.marker2DIn3DVersion.position.y);
             selected.marker3D.position = new Vector2(selected0.marker3D.position.x - Range
             [i - 1], 
             selected0.marker3D.position.y);
         }
         else if(i == 5)
         {
             ObjectStat selected3 = selectedUnits[3].GetComponent<ObjectStat>();
             
             selected.marker2DIn3DVersion.position = new 
             Vector2(selected3.marker2DIn3DVersion.position.x + Range[i - 1], 
             selected3.marker2DIn3DVersion.position.y);
             selected.marker3D.position = new Vector2(selected3.marker3D.position.x + Range
             [i - 1], 
             selected3.marker3D.position.y);
         }
         else if(i == 6)
         {
             ObjectStat selected3 = selectedUnits[3].GetComponent<ObjectStat>();
             
             selected.marker2DIn3DVersion.position = new 
             Vector2(selected3.marker2DIn3DVersion.position.x - Range[i - 1], 
             selected3.marker2DIn3DVersion.position.y);
             selected.marker3D.position = new Vector2(selected3.marker3D.position.x - Range
             [i - 1], 
             selected3.marker3D.position.y);
         }
         else if(i == 7)
         {
             ObjectStat selected5 = selectedUnits[5].GetComponent<ObjectStat>();
             
             selected.marker2DIn3DVersion.position = new 
             Vector2(selected5.marker2DIn3DVersion.position.x + Range[i - 1], 
             selected5.marker2DIn3DVersion.position.y);
             selected.marker3D.position = new Vector2(selected5.marker3D.position.x + Range
             [i - 1], 
             selected5.marker3D.position.y);
         }
         else if(i == 8)
         {
             ObjectStat selected6 = selectedUnits[6].GetComponent<ObjectStat>();
             
             selected.marker2DIn3DVersion.position = new 
             Vector2(selected6.marker2DIn3DVersion.position.x - Range[i - 1], 
             selected6.marker2DIn3DVersion.position.y);
             selected.marker3D.position = new Vector2(selected6.marker3D.position.x - Range
             [i - 1], 
             selected6.marker3D.position.y);
         }
 }