tesam tu sat pradhananam
dharmo namosana tasya
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Among these many sons, six were the foremost, such as Prthusrava and Prthukirti. The son of Prthusrava was known as Dharma, and his son was known as Usana. Usana was the performer of one hundred horse sacrifices.