The ornamental design for a receptacleblank, as shown and described.
FIG. 1 is a plan view of the receptacle blank;
FIG. 2 is a front elevational view of the receptacle blank; and,
FIG. 3 is a right side elevational view of the receptacle blank, the left side elevational view being a mirror image of the right side elevational view shown.
The unshaded circular shapes shown in FIG. 1 depict apertures on the receptacle blank and the shaded circular shapes shown in FIG. 1 depict depressions formed on the receptacle blank.