We have given,
a1 = - 1 , an =

an−1

n

, n ≥ 2
a1 = - 1 , a2 =

a1

2

= −

1

2

, a3 =

a2

3

=

(− 1 2 )

3

= −

1

6

a4 =

a3

4

=

(− 1 6 )

4

= −

1

24

, a5 =

a4

5

=

(− 1 24 )

5

= −

1

120

Hence the first five terms of the given sequence are – 1, – 1/2, – 1/6, –1/24, –1/120.
The corresponding series is
- 1 + (−

1

2

)+(−

1

6

) + (−

1

24

)+(−

1

120

) + ...