Pascal's Triangle

DESCRIPTION:

In mathematics, Pascal's triangle is a triangular array of the binomial coefficients expressed with formula

(nk)=n!k!(n−k)!\lparen {n \atop k} \rparen = \frac {n!} {k!(n-k)!}(kn​)=k!(n−k)!n!​

where n denotes a row of the triangle, and k is a position of a term in the row.

You can read Wikipedia article on Pascal's Triangle for more information.

Task

Write a function that, given a depth n, returns n top rows of Pascal's Triangle flattened into a one-dimensional list/array.

Example:

n = 1: [1]
n = 2: [1,  1, 1]
n = 4: [1,  1, 1,  1, 2, 1,  1, 3, 3, 1]

---

def pascals_triangle(n):
    if n==1:
        return [1]
    elif n==2:
        return [1,1,1]
    ans=[1, 1,1]
    alist=[1,1]
    templist=[]
    for i in range(n-2):
        templist.append(1)
        for i in range(len(alist)-1):
            templist.append(alist[i]+alist[i+1])
        templist.append(1)
        alist=templist.copy()
        for i in alist:
            ans.append(i)
        templist=[]
    return ans