The [,]
syntax creates multidimensional arrays, not jagged arrays. For the latter, you would need to do this:
int n = 4;
string[][] table = new string[n][];
for (int i = 0; i < n; i++)
table[i] = new string[n-i];
Btw. you really don’t want to decrement n
while looping in a loop with the condition i < n
(or i <= n
).