Abstract
The behavior of a considerable number of physical phenomena is described by periodic bifurcating solutions of quadratic Ordinary Differential Equations. The purpose of this paper is to present an algorithm consisting of a combination of Power series and Fourier Series (PES) which reduces the problem of solving the differential equations to a recursive sequence of linear algebraic ones. This algorithm is based on two theorems that, with easily verifiable algebraic conditions, ensure the existence of such solutions.