Fill the missing value in this series:
1BDF, H3JL, NP5R, ?

Let's split each token cluster to find the component patterns:
1. First Letter position pattern: $\text{B}(2)\to \text{H}(8)\to \text{N}(14)\to ?$
The pattern is adding $+6$. Next first letter is $14+6=20\to \text{T}$.
2. Number position pattern: $1\to 3\to 5\to ?$ (consecutive odd numbers). Next number is $7$. Notice that the index location of the digit shifts progressively from left to middle to right, then wraps back to the left.
3. Remaining alphabet pairs:
* Cluster 1: $\text{DF}\to \text{D}(4),\text{F}(6)$
* Cluster 2: $\text{JL}\to \text{J}(10),\text{L}(12)$
* Cluster 3: $\text{PR}\to \text{P}(16),\text{R}(18)$
The letters increase by $+2$ internally and jump by $+4$ from cluster to cluster. Following $\text{R}(18)$, the next starting letter is $18+4=22\to \text{V}$, and the subsequent letter is $22+2=24\to \text{X}$.

Assembling the pieces with the digit positioned at the end gives TVX7.