Same entry in other lexica; the headword is evidently quoted from somewhere.
The thematic verb οἰγνύω is a regularization of the athematic οἴγνυμι ; earlier thematic forms occur with the stem οἰγ- . For either athematic or thematic forms, the compound with ἀν- is more frequent. See LSJ entry at web address 1, and other forms of this verb at omega 11, omega 38, omega 39.