Non-viability of gravitational theory based on a quadratic lagrangian

It is shown that physically reasonable solutions of the field equations based on an R2 lagrangian are possible. (R is the scalar curvature.) However, it is shown that experimental predictions of such a theory are at variance with observations. The most general quadratic lagrangian is also considered and it is shown that the R2 term must dominate thus invalidating gravitational equations based on a general quadratic lagrangian.