Theorem. Any entire function of order less than 1 has its Newton's expansion converging.
Proof.
Let

be entire of order less than

, so

,

. Write the Newton polynomial

Note that

for

. On the other hand, we can crudely estimate

in a disk of radius

by

.
Now,
![$\frac 1{k!}|\Delta^k f(0)|\le \max_{[0,R/2]}\frac{|f^{(k)}|}{k!}\le (2/R)^k Ce^{R^p}$ $\frac 1{k!}|\Delta^k f(0)|\le \max_{[0,R/2]}\frac{|f^{(k)}|}{k!}\le (2/R)^k Ce^{R^p}$](https://dxdy-01.korotkov.co.uk/f/8/e/2/8e24374f9dbd57182f9bd7e43dedb12982.png)
by Cauchy, so we finally get

in the disk of radius

centered at the origin.
Now, for

, each corresponding Blaschke factor

is at most

in absolute value, so

Choosing

, we get

as

.
Собственно говоря, не понимаю ни хрена.