1, 1, 2, 5, 15, 51, 191, 780, 3440, 16249, 81736, 435796, 2453100, 14529728, 90294625, 587256087, 3988153356, 28223370977, 207745253237, 1587804229045, 12581186077773, 103197641796678, 875085283793768, 7661468372063681, 69173450911547978, 643354845906697516