Ya, so there is a point(q) starting with coordinates xq and yq. Three other points a, b, and c have there x and y coordinates labelled in the same manner. A, b, and c exert a "push" on q each second suppose, and move it to the endpoint of a vector 2 times the magnitude of vector a,b, or c to q. The direction remains the same and the origin of the vector is still a,b or c. The average of the endpoints created by these vectors, 1 for a, 1 for b, and1 for c, gives q's position after 1 second. After n times though q's position would be the average of all these averages.
I derived the sum to n