  The paper concerns the ground state structure of the partly filled l-shell of
a fermionic gas of atoms of spin s in a spherically symmetric spin independent
trap potential. At particle numbers N=n(2s+1), n=1,2,...,2l+1 the basic
building blocks are clusters consisting of (2s+1) atoms, whose wave functions
are completely symmetric and antisymmetric in space and spin variables,
respectively. The creation operator of a cluster is constructed whose repeated
application to the vacuum leads to the multi-cluster state. Ground state energy
expressions are derived for the n-cluster states at different l,s values and
interpreted in simple terms.
