2 A sequence is defined as follows.
\(u _ { 1 } = a\), where \(a > 0\)
To obtain \(u _ { r + 1 }\)
- find the remainder when \(u _ { r }\) is divided by 3 ,
- multiply the remainder by 5 ,
- the result is \(u _ { r + 1 }\).
Find \(\sum _ { r = 2 } ^ { 4 } u _ { r }\) in each of the following cases.
- \(a = 5\)
- \(a = 6\)