"If you read my previous post about hexagonal maps: Understanding hexagonal tiles – updated with HTML5 examples thanks to Phaser, you will see there are two ways of representing hexagonal maps and finding which tile you can find at a generic x,y coordinate, according to the way hexagons are placed on the map."
"When we need to find adjacent tiles of a given tile in an hexagon map, things get even more difficult because there are some things to consider if hex maps have a even or odd number of rows and columns."