  As a model for a deformed nucleus the many level pairing model (picket fence
model with ~100 levels) is considered in four approximations and compared to
the exact solution given by Richardson long time ago. It is found that, as
usual, the number projected BCS method improves over standard BCS but that it
is much less accurate than the more sophisticated many-body-approaches which
are Coupled Cluster Theory (CCT) in its SUB2 version or Self-Consistent Random
Phase Approximation (SCRPA).
