Engine comprising a propeller unit with a pair of contrarotating propellers (31, 32), a gas generator (5) supplying a power turbine (53), the pair of propellers being rotationally driven by the shaft (53A) of the power turbine via a speed reduction gearbox, the axis of rotation (XX) of the pair of propellers not being coaxial with that (YY) of the power turbine, the speed reduction gearbox comprising a differential gearset (7) and a first stage (6) comprising a simple gearset connecting the turbine shaft (53A) and the differential gearset (7), the engine air intake comprising an air intake duct (11), the air intake duct (11) being in the shape of a lobe adjacent to the assembly formed by the simple gearset and the differential gearset (7).