"Ogóó tí a kó rí ara wa" (pronounced "O-goh-oh ti a koh ree ah-ra wah")
This literally translates to "Long time we did not see each other."
More informal options:
* "A ti pé" (pronounced "Ah ti peh") - "It has been a while"
* "Ó tí pé" (pronounced "Oh ti peh") - "It's been a while"
You can also use a greeting followed by "o ti pé" like:
* "E káa bò" o ti pé (pronounced "Eh ka-ah boh, oh ti peh") - "How are you? It's been a while"
* "Bawo ni?" o ti pé (pronounced "Bah-woh ni? Oh ti peh") - "How are you? It's been a while"
The choice of phrase depends on the context and your relationship with the person you are talking to.