I_3

using System;
using static AngouriMath.MathS;

Console.WriteLine(I_1.ToString(multilineFormat: true));
Console.WriteLine(I_2.ToString(multilineFormat: true));
Console.WriteLine(I_3.ToString(multilineFormat: true));
Console.WriteLine(I_4.ToString(multilineFormat: true));

Matrix[1 x 1]
1   
Matrix[2 x 2]
1   0   
0   1   
Matrix[3 x 3]
1   0   0   
0   1   0   
0   0   1   
Matrix[4 x 4]
1   0   0   0   
0   1   0   0   
0   0   1   0   
0   0   0   1