The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 15 |
| 5 | 31 |
| 6 | 92 |
| 7 | 267 |
| 8 | 1023 |
| 9 | 4404 |
| 10 | 21705 |
| 11 | 116999 |
| 12 | 680790 |
| 13 | 4217693 |
| 14 | 27653099 |
| 15 | 190915798 |
| 16 | 1382993235 |
| 17 | 10480207683 |
| 18 | 82865009684 |
| 19 | 682077068303 |
| 20 | 5832742772351 |
| 21 | 51724159284888 |
| 22 | 474869818486877 |
| 23 | 4506715742641627 |
[1,3,6,15,31,92,267,1023,4404,21705,116999,680790, 4217693,27653099,190915798,1382993235,10480207683, 82865009684,682077068303,5832742772351, 51724159284888,474869818486877,4506715742641627] |