The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 52 |
| 6 | 203 |
| 7 | 674 |
| 8 | 2066 |
| 9 | 6184 |
| 10 | 18587 |
| 11 | 56867 |
| 12 | 178317 |
| 13 | 561319 |
| 14 | 1760125 |
| 15 | 5489888 |
| 16 | 17057701 |
| 17 | 52931331 |
| 18 | 164466672 |
| 19 | 511758485 |
| 20 | 1593612234 |
| 21 | 4962950389 |
| 22 | 15451453190 |
| 23 | 48088784307 |
| 24 | 149640967002 |
| 25 | 465653853729 |
| 26 | 1449146745582 |
| 27 | 4510183339086 |
| 28 | 14037494547193 |
[1,1,2,5,15,52,203,674,2066,6184,18587,56867, 178317,561319,1760125,5489888,17057701,52931331, 164466672,511758485,1593612234,4962950389, 15451453190,48088784307,149640967002,465653853729, 1449146745582,4510183339086,14037494547193] |