https://bitcointalksearch.org/topic/ann-powposerc20-powadv-mineable-ethereum-token-3180092
https://github.com/PoWAdv
// the number of coins owned
uint256 minerBalance = uint256(balanceOf(solver));
if(minerBalance <= 2 * _BLOCK_REWARD)
return getMiningTarget();
// the number of full block rewards owned
uint256 minerDiscount = uint256(minerBalance.div(_BLOCK_REWARD));
discountedDiff = miningTarget.mul(minerDiscount.mul(minerDiscount));
if(discountedDiff > _MAXIMUM_TARGET) //very easy
discountedDiff = _MAXIMUM_TARGET;
return discountedDiff;
}