Charles Ellicott Commentary 1 Chronicles 9:44

"And Azel had six sons, whose names are these: Azrikam, Bocheru, and Ishmael, and Sheariah, and Obadiah, and Hanan: these were the sons of Azel." — 1 Chronicles 9:44 (ASV)

With the omission of the sons of Eshek and Ulam here, compare the similar abridgment of the list in 1 Chronicles 6:4–15, when repeated in 1 Chronicles 6:50–53. This suggests that the present omission is not due to inadvertence, but either to the chronicler's design or to a similar omission in his source.