Question 484301
Number of different one-to-one correspondences that could be listed between the vertices of two regular triangles is given by Sigma (2*3 -- 1) = Sigma n (from 1 to 5) = 15 

Number of different one-to-one correspondences that could be listed between the vertices of two regular n-gons is given by Sigma n (from 1 to 2n -- 1) = n(2n -- 1)