The first few terms of this sequence are 1,1,2,4,10,26,76,232; these numbers are called the telephone numbers, and they also count the number of Young tableaux with a given number of cells.
The first few terms of this sequence are 1,1,2,4,10,26,76,232. This recurrence relation, which was found by Heinrich August Rothe in 1800, also counts the number of Young tableaux with a given number of cells.