Questions & Answers about Я написал адрес по памяти, но потом проверил его.
Both verbs are past tense masculine singular forms.
- написал = wrote
- проверил = checked / verified
In Russian past tense, the form agrees with the subject in gender and number:
- написал = masculine
- написала = feminine
- написало = neuter
- написали = plural
Since the speaker is understood as masculine here, the sentence uses написал and проверил. If the speaker were female, it would be:
Я написала адрес по памяти, но потом проверила его.