“…In [1], several graph-theoretic properties of I(n, j, k) such as connectedness, girth, being bipartite or being vertex-symmetric, are characterized in terms of number-theoretic properties of parameters n, j, k. An algorithm for deciding which sets of parameter values give rise to isomorphic I-graphs is also given there. In [5], the following result (crucial for our enumeration) is proved: Theorem 1.1. I(n, j, k) and I(n, j , k ) are isomorphic if and only if there exists an integer a, relatively prime to n, such that either {j , k } = {aj mod n, ak mod n} or {j , k } = {aj mod n, −ak mod n}.…”