Let
S
S
be the class of functions
f
(
z
)
=
z
+
⋯
f(z) = z + \cdots
analytic and univalent in the unit disk
D
D
. For
f
(
z
)
=
z
+
a
2
z
2
+
⋯
∈
S
f(z) = z + {a_2}{z^2} + \cdots \in S
, Zalcman conjectured that
|
a
n
2
−
a
2
n
−
1
|
≤
(
n
−
1
)
2
(
n
=
2
,
3
,
…
)
|a_n^2 - {a_{2n - 1}}|\; \leq \;{(n - 1)^2}(n = 2,3, \ldots )
. This conjecture is verified for
n
≥
4
n \geq 4
and close-to-convex functions.