  We consider numerical semigroups $S_3 = \langle d_1,d_2,d_3 \rangle$,
minimally generated by three positive integers. We revisit the Wilf question in
$S_3$ and, making use of identities for degrees of syzygies of such semigroups,
give a short proof of existence of an affirmative answer. We find also the
lower bound for Frobenius numbers of $S_3$ and upper and lower bounds for
higher genera.
