Lambert series

== English == === Etymology === Named for Johann Heinrich Lambert. === 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}}}.}