Write a computer function to calculate the nth row of pascal's triangle iteratively from the (n-1)-st row. (the computation step, using vector operations, can be done in one line).

only #2 represents an object at rest on a table.

in #1, there is no normal force due to the table; the object is accelerating downward.

in #3, the vertical forces are not balanced; the object is accelerating downward.

in #4, neither the vertical nor the horizontal forces are balanced. the object is accelerating upwards and to the right.

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