Name: n-node tree graphs with diagonals - related to pseudopolyominoes. Comments: I would like to know how this sequence is defined! - njas So would I!!! Jon Perry perry at globalnet.co.uk http://www.users.globalnet.co.uk/~perry/maths/ http://www.users.globalnet.co.uk/~perry/DIVMenu/ BrainBench MVP for HTML and JavaScript http://www.brainbench.com