Ask the database for the lowest fare, and that's a new search function - ask for lowest fare on all destinations (since you don't care) and that is a huge processing task.... your best bet is narrow your search down a bit, and use the airlines that have "fares by month" grids (bmibaby and easyJet to name but two)...
I understand where you are coming from. Put one grain of sand on the first square of a chessboard and double up on the remaining squares.....see how many grains of sand you'll have on the 64th square!
I do have City+Guilds L3 qualification in web design and I thought a simple database query was difficult enough!
However, going back to my original grouse, skyscanner provided a good service. As an earlier poster said, Ryanair seems to have shot itself in the foot.
I will look at the bmibay and easyjet 'fares by the month' features on their websites.