Find the odd one out in the series: B4, D16, F38, H64, J100

Let's analyze the positions of the letters in the alphabetical sequence along with their corresponding numbers:
* $\text{B}=2⟹2^2=4⟹\text{B}4$
* $\text{D}=4⟹4^2=16⟹\text{D}16$
* $\text{F}=6⟹6^2=36$ (but given as $\text{F}38$)
* $\text{H}=8⟹8^2=64⟹\text{H}64$
* $\text{J}=10⟹10^2=100⟹\text{J}100$

The rule specifies that the number should be the square of the alphabetical position of the letter. $\text{F}38$ breaks this pattern as $6^2=36$. Therefore, $\text{F}38$ is the odd one out.