c
k
= [(
-
1)
k
-
1]
/
(
k
2
)
, jos
k
0
;
c
0
=
/
2
; °
a
k
= 2[(
-
1)
k
-
1]
/
(
k
2
)
, jos
k
0
;
a
0
=
;
b
k
= 0
.