Noun
Lambert series (plural Lambert series)
(mathematics) A series taking the form
S
(
q
)
=
∑
n
=
1
∞
a
n
q
n
1
−
q
n
.
{\displaystyle S(q)=\sum _{n=1}^{\infty }a_{n}{\frac {q^{n}}{1-q^{n}}}.}