When I do this via Python, I get 1,4,6,4,1 which I know is row 4 of Pascal's Triangle (and n=4 so is that a coincidence or does it line up with the 4th row). When it says "confirm that it gives you what you expect", what am I looking for here? A connection between row 4 of Pascal's Triangle? Thank you

Exercise 3.1 If we expand out the binomial (a +b) we get n n! (a + b)" = abner " = { bn r!(n-r)! r=0 4 and confirm that it Evaluate the terms in the sum on the right hand side for the case n gives you what you expect