Sequences and series question.

Hi guys, rhe following is a question that I busted my brains over, but could not get, so help would be greatly appreciated.

And I don't know how to properly use latex, so please bear with me.

Q) A sequence satisfies with = 3 and = 2.

Find and

Also, T1=2 and T2=7

Question without latex: A sequence satisfies [term 'n' = 0.5*[term 'n-1' + term 'n+1']. Find term's 3 and 4.

Sorry I have absolutely no idea how to do this, one, also my latex skills are pretty poor, so ANY HELP WOULD BE GREATLY APPRECIATED.