EN
The relationship between Liouville's arithmetic identities and products of Lambert series is investigated. For example it is shown that Liouville's arithmetic formula for the sum
$∑_{{(a,b,x,y) ∈ ℕ ⁴ \atop ax+by=n}} (F(a-b) - F(a+b))$,
where n ∈ ℕ and F: ℤ → ℂ is an even function, is equivalent to the Lambert series for
$(∑_{n=1}^{∞} (qⁿ/(1-qⁿ))sin nθ)²$ (θ ∈ ℝ, |q| < 1)
given by Ramanujan.