  For pure symmetric 3-qubit states there are only three algebraically
independent entanglement measures; one choice is the pairwise concurrence
$\mathcal C$, the 3-tangle $\tau$, and the Kempe invariant $\kappa$. Using a
canonical form for symmetric $N$-qubit states derived from their Majorana
representation, we derive the explicit achievable region of triples $(\mathcal
C,\tau,\kappa)$.
