  We study small clusters of bosons, $A=2,3,4,5,6$, characterized by a resonant
interaction. Firstly, we use a soft-gaussian interaction that reproduces the
values of the dimer binding energy and the atom-atom scattering length obtained
with LM2M2 potential, a widely used $^4$He-$^4$He interaction. We change the
intensity of the potential to explore the clusters' spectra in different
regions with large positive and large negative values of the two-body
scattering length and we report the clusters' energies on Efimov plot, which
makes the scale invariance explicit. Secondly, we repeat our calculation adding
a repulsive three-body force to reproduce the trimer binding energy. In all the
region explored, we have found that these systems present two states, one deep
and one shallow close to the $A-1$ threshold, and scale invariance has been
investigated for these states. The calculations are performed by means of
Hyperspherical Harmonics basis set.
