The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 42 |
| 5 | 248 |
| 6 | 1570 |
| 7 | 10416 |
| 8 | 71474 |
| 9 | 503088 |
| 10 | 3612226 |
| 11 | 26353720 |
| 12 | 194806458 |
| 13 | 1455874792 |
| 14 | 10982013250 |
| 15 | 83504148192 |
| 16 | 639360351074 |
| 17 | 4925190101600 |
| 18 | 38144591091970 |
| 19 | 296837838901992 |
| 20 | 2319880586624714 |
| 21 | 18200693844341720 |
| 22 | 143294043656426082 |
| 23 | 1131747417739664528 |
[1,2,8,42,248,1570,10416,71474,503088,3612226, 26353720,194806458,1455874792,10982013250, 83504148192,639360351074,4925190101600, 38144591091970,296837838901992,2319880586624714, 18200693844341720,143294043656426082, 1131747417739664528] |