Number pattern using for loop.

How to create below pattern using for loops in C#
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1

 

What is the formula that creates those number sequences?

 

Starting 1 and ending 1 is compulsory and second step is addition of above number one by one like this:
1 1
(1) 1+1 = 1 2 1
(2) 1+2, 2+1 = 1 3 3 1
(3) 1+3, 3+3, 3+1 = 1 4 6 4 1
(4) 1+4, 4+6, 6+4, 4+1 = 1 5 10 10 5 1