Hodge numbers for orbifolds of Calabi-Yau threefolds Ferma type and the Roan pairs

First, for orbifolds of Calabi-Yau threefolds of Ferma type, we define Roan’s Hodge numbers. We prove, Theorem 5.2, that for all orbifols of Calabi-Yau threefolds Ferma type, Roan’s Hodge numbers correctly count the stringy Euler numbers due to Vafa formula. Second, for Calabi-Yau threefolds Ferma type, we apply Roan’s Hodge numbers to get a relation between the Borcea-Voisin construction [Borcea, Voisin] and Betglund-Hübsch-Krawits mirror duality.