The name de Moivre polynomial is used for two unrelated families of polynomials, one in combinatorics and the other in the theory of algebraic equations.
In the combinatorial usage, the de Moivre polynomials are the ordinary partial Bell polynomials (O'Sullivan 2022). For nonnegative
integers
and
, they are defined by the formal
power series identity
|
(1)
|
Thus
is the coefficient of
in the
th power of a formal
power series with its
coefficient equal to 0.
The boundary values are
,
for
, and
for
. For
, the relation to the exponential partial
Bell polynomial is
|
(2)
|
For example, . Multiplication of
the defining formal power series gives the
recurrence relation
|
(3)
|
where
and
(Comtet 1974, O'Sullivan 2022).
In the algebraic usage, a de Moivre polynomial is a shifted, scaled Chebyshev polynomial of the first kind. For an odd number , one normalization is
|
(4)
|
where
and
are nonzero rational numbers, and
has no rational square root. Here
is the Chebyshev
polynomial of the first kind. The square roots
cancel, leaving rational coefficients,
and the equation
can be solved using radicals
(Girstmair 2022). For
, it becomes
|
(5)
|
which has the form of de Moivre's quintic with
and
.