Sp200,   That would not be a supported configuration since the other dimms are larger. As seen on page 81 here, the larger dimms must be populated first.You can also find the other memory population guidelines there as well.   Let me know if this helps.  
Dell PowerEdge R730. System has two Intel(R) Xeon(R) CPU E5-2687W v4 @ 3.00GHz processors and the following memory. A1 16.00 GBA2 32.00 GBA3 32.00 GBA4 32.00 GBA5 16.00 GBA6 16.00 GBA7 16.00 GBA8 16.00 GBA9 16.00 GBA10 16.00 GBA11 16.00 GBA12 16.00 GBB1 32.00 GBB2 32.00 GBB3 32.00 GBB4 32.00 GBB5 16.00 GBB6 16.00 GBB7 16.00 GBB8 16.00 GBB9 16.00 GBB10 16.00 GBB11 16.00 GBB12 16.00 GB Is the 16GB module in A1 a valid configuration ? Would the module in be causing system issues ?
Poweredge R730 Memory configuration