>>> def triangles(max):

...   L = [1]

...   print(L)

...   for i in range(1,max):

...     L = [1] +[L[i]+L[i+1] for i in range(len(L)-1)] + [1]

...     yield L

...

>>> for t in triangles(10):

...   print(t)

...

[1]

[1, 1]

[1, 2, 1]

[1, 3, 3, 1]

[1, 4, 6, 4, 1]

[1, 5, 10, 10, 5, 1]

[1, 6, 15, 20, 15, 6, 1]

[1, 7, 21, 35, 35, 21, 7, 1]

[1, 8, 28, 56, 70, 56, 28, 8, 1]

[1, 9, 36, 84, 126, 126, 84, 36, 9, 1]

>>>