Rk. Parui et al., EXACT ENERGY EIGENVALUES FOR THE DOUBLY ANHARMONIC-OSCILLATOR, International journal of theoretical physics, 33(3), 1994, pp. 613-615
The exact energy eigenvalues for the potential V(r) = 1/2omega2r2 + 1/
4lambdar4 + 1/6etar6 and the conditions for their occurrence have been
determined.