We have given, $a_1$ = $a_2$ = 2 , $a_n$ = $a_{n-1}$ - 1 , $a_1$ = 2 , $a_2$ = 2 , $a_3$ = $a_2$ - 1 = 2 - 1 = 1, $a_4$ = $a_3$ - 1 = 1 - 1 = 0 and $a_5$ = $a_4$ - 1 = 0 - 1 = - 1 Hence the first five terms of the given sequence are 2, 2, 1, 0, – 1. The corresponding series is 2 + 2 + 1 + 0 + (– 1) + .......