A primitive -series
is a Dirichlet L-series
whose number
theoretic character
modulo
is primitive. This means that its conductor equals
, so it is not induced by a number
theoretic character of any proper divisor of
.
If
is induced by a primitive number theoretic
character
of conductor
dividing
,
then
Thus every imprimitive Dirichlet -series differs from a unique primitive one by finitely many
Euler factors. Primitive
-series are therefore the basic factors in the decomposition
of Dirichlet
-functions.