The Ethereum Yellow Paper includes on page 6 in equation (44) a term which contributes to the difficulty of a block. This term is added to the difficulty in equation (39).
is an exponential function which depends on the length of the block chain only. The longer the chain up to the current block , the higher and 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 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 instead of the chain length ?