Question

A sequence {an} is generated by the recursive formulas a1 = 5 and an = an-1 + 5(-1)n. Find, a343, the 343rd term of the sequence

Answer 1

\(a_n= a_{n-1}+5(-1)^n\) , right?

Answer 2

Since you don't reply, I don't know whether the problem is in correct format or not. I give you a hint:
calculate \(a_2, a_3,a_4, a_5\) you can see what happen with the results. I mean when n is odd, \(a_n\) = ....., when n is even, \(a_n \) =.....
then you have the answer for \(a_{343}\)