The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 21 |
| 6 | 59 |
| 7 | 125 |
| 8 | 349 |
| 9 | 848 |
| 10 | 2224 |
| 11 | 5210 |
| 12 | 15720 |
| 13 | 37096 |
| 14 | 98241 |
| 15 | 245251 |
| 16 | 684475 |
| 17 | 1703174 |
| 18 | 4915084 |
| 19 | 12024901 |
| 20 | 33594399 |
[1,1,2,4,10,21,59,125,349,848,2224,5210,15720, 37096,98241,245251,684475,1703174,4915084, 12024901,33594399] |