  The SS-HORSE-NCSM method is generalized to the case of democratic decay into
an odd number of fragments. This method is applied to the search for resonances
in three-neutron system (trineutron) using ab initio No-Core Shell Model
calculations with realistic nucleon-nucleon potentials. The $3/2^-$ and $1/2^-$
strongly overlapping resonances are predicted when softened $NN$ interactions
are used and are preferred over the case where bare $NN$ interactions of the
chiral effective field theory are used with no resonance obtained.
