Current taken from the combination of n cells each of internal resistance r in series with externaI resistance R is $ i = \frac{nE}{nr + R} $
Similarly, for paralleI combination $ i = \frac{nE}{r + nR} $
For mixed grouping of n such cell in m rows with externaI resistance R is $ i = \frac{mnE}{mR + nr} $
It is obvious that maximum current obtained from each combination depends on relative vaiues of external and internaI resistance.