The connection between a three-dimensional hydrogenlike atom and a pair of coupled two-dimensional harmonic oscillators is established by applying the Jordan-Schwinger boson calculus to the algebra of the Runge-Lenz-Laplace-Pauli vector. The dynamical groupSO4,2 of the three-dimensional hydrogen atom arises as a quotient of the groupSp8R associated to a four-dimensional harmonic oscillator with constraint.