  Blue straggler stars (BSS) are peculiar objects which normally appear as a
single broad sequence along the extension of the main sequence. Only four
globular clusters (GCs) have been observed to have two distinct and parallel
BSS sequences. For the first time for any open cluster (OC), we report double
BSS sequences in Berkeley 17. Using the machine-learning based membership
algorithm ML-MOC on Gaia EDR3 data, we identify 627 cluster members, including
21 BSS candidates out to 15 arcmin from the cluster center. Both the BSS
sequences are almost equally populated and parallel to one another in Gaia as
well as in Pan-STARRS colour-magnitude diagram (CMD). We statistically confirm
their presence and report that both BSS sequences are highly segregated
compared to the reference population out to $\sim$5.5 arcmin and not segregated
thereafter. The lower densities of OCs make BSS formation impossible via the
collisional channel. Therefore, mass transfer seems to be the only viable
channel for forming candidates of both sequences. The gap between the red and
blue BSS sequences, on the other hand, is significant and presents a great
opportunity to understand the connection between BSS formation and internal as
well as external dynamics of the parent clusters.
