  In this paper, we investigate the early-time optical$-$near-infrared (NIR)
spectral energy distributions (SEDs) of four Type Ibn supernovae (SNe). We find
that the SEDs of SN~2010al, LSQ13ddu, and SN~2015G can be well explained by the
single-component blackbody model, while the SEDs of OGLE-2012-SN-006 cannot. We
invoke the double-component model assuming that the SEDs were produced by the
SN photosphere and the heated dust to fit the optical$-$NIR SEDs of the four
SNe Ibn, finding that the derived temperatures of the dust associated with
OGLE-2012-SN-006 favor the scenario that the dust consists of the graphite
grains, and the mass and temperature of dust are
$\sim$$0.5-2.0\times10^{-3}~M_\odot$ and $\sim$ $1200-1300$ K, respectively.
Moreover, our fits for SN~2010al, LSQ13ddu, and SN~2015G show that the upper
limits of the masses of the dust associated with the three SNe Ibn are
respectively $1.45\times 10^{-5}~M_\odot$, $5.9\times 10^{-7}~M_\odot$, and
$2.4\times 10^{-7}~M_\odot$. A further analysis demonstrates that the inferred
radius of the dust shell surrounding OGLE-2012-SN-006 is significantly larger
than that of the SN ejecta at early epochs, indicating that the NIR excesses of
the SEDs of OGLE-2012-SN-006 were produced by a preexisting dust shell. Our
study for the early-time SEDs of four SNe Ibn, together with the previous
studies and the fact that some SNe showed the evidence of dust formation at the
late-time SEDs, indicates that at least $\sim$1/3 of SNe Ibn show evidence for
dust formation.
