First of all, we DO NOT say 'Dang seen' to friends. Second of all, I'd like you to think of a, i, e, o as romanized Japanese when you see my romanization. And I also romanize ㅓ as u/uh (u of run), ㅜ as oo(oo of soon). Lastly I'm not exactly sure what you meant by it, but you will find out after seeing this.
Nice to meet you = Man na suh bang gap seumnida [Formal]
= Man na suh bang ga wuh yo [Informal]
= Man na suh bang ga wuh [Between close friends]
People say this when they first meet someone.
Nice meeting you = Man na suh bang ga wut sseum nida [Formal]
Man na suh bang ga wut ssuh yo [Informal]
Man na suh bang ga wut ssuh [Between close friends]
It's what people say when they're leaving.