# Difficulty growing exponentially with block chain length?

The Ethereum Yellow Paper includes on page 6 in equation (44) a term $\epsilon$ which contributes to the difficulty of a block. This term is added to the difficulty in equation (39).

${\epsilon \equiv {\left \lfloor{2 ^ {\left \lfloor {H_i \div 100000} \right \rfloor - 2 } }\right \rfloor}$

$\epsilon$ is an exponential function which depends on the length of the block chain only. The longer the chain up to the current block ${H_i}$, the higher $\epsilon$ and $\epsilon$ is growing exponentially.

This looks very strange. It would mean that the longer the chain, the higher the difficulty and the more difficult and costly it becomes to mine a new block. This is counter intuitive.

Does $\epsilon$ really depend on the length of the block chain? Or is this a typo on in the paper and should it actually depend on something else, i.e. the gas limit ${H_l}$ instead of the chain length ${H_i}$?