Try using a Jagged array. The Basic syntax is something like:
int[][] arr = new int[5][];
for (int row = 1; row <= 5; row++)
{
arr[row - 1] = new int[row];
for (int col = 0; col < row; col++)
{
arr[row - 1][col] = col + 1;
}
}
This creates a structure like this:
1
12
123
1234
12345