All processes run in Spatial Analyst adhere to the analysis environment settings. In cases where the output cell size is larger than the input cell size, the input is resampled to this larger cell size before any map algebra is applied. The resampling method used is nearest neighbor.
In situations where multiple cell centers are equidistant to the center of the output cell, the last value encountered in a scanning process is applied to the output cell. The scanning of the input cells starts in the upper left, moves to the right, then goes down a row, and ends in the lower right.
In a case where the larger cell size is exactly twice the size of the input and the extents are the same, the cell in the lower right is used in the nearest neighbor resampling. If the analysis extents are set so that the output is shifted diagonally from the input, the cell that is closest to the center of the output cell center has its value assigned to the output cell.