Cross reference
Genesis 38:4
4 And again she gave birth to a son, and he gave him the name Onan.
Genesis 46:12
12 And the sons of Judah: Er and Onan and Shelah and Perez and Zerah: but Er and Onan had come to their death in the land of Canaan; and the sons of Perez were Hezron and Hamul.
Numbers 26:19
19 The sons of Judah, Er and Onan: and Er and Onan had come to their death in the land of Canaan.