On the functional equation ๐(๐ก)=๐(๐ก)-๐(2๐ก)
On the functional equation ๐(๐ก)=๐(๐ก)-๐(2๐ก)
is necessary and sufficient for the existence of a periodic (of period 1) function gCL(,1) such that (2) f(t) = g(t) g(2t). This theorem, without the assertion that geL',1) was apparently established by R. Fortet in his paper [1 ] though his proof is not clear to me. A proof โฆ