First, I want to say you, congratulation! You are the luckiest person, that you have an approved account of google Adsense, but it seemes very uncommon that you want to sell your golden egg’s hen in exchange of some coins.
As i can see, you have an ability to understand the Googles rule because you have an approved account in your hand. You can make more money through blog writing or create some useful videos for YouTube, insted of sell your approved Adsense account to others.
As per Googles norms you can’t transfer or sell your Adsense account to others.
But you can try to sell it through social media network.