The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 61 |
| 6 | 206 |
| 7 | 736 |
| 8 | 2634 |
| 9 | 9720 |
| 10 | 36024 |
| 11 | 135994 |
| 12 | 516030 |
| 13 | 1981642 |
| 14 | 7648260 |
| 15 | 29764416 |
| 16 | 116364138 |
| 17 | 457689632 |
| 18 | 1807445576 |
| 19 | 7170850408 |
| 20 | 28548301000 |
| 21 | 114073426233 |
| 22 | 457173621678 |
| 23 | 1837717521408 |
| 24 | 7406075729478 |
| 25 | 29921472956312 |
| 26 | 121154164282920 |
| 27 | 491604207872268 |
[1,1,2,6,18,61,206,736,2634,9720,36024,135994, 516030,1981642,7648260,29764416,116364138, 457689632,1807445576,7170850408,28548301000, 114073426233,457173621678,1837717521408, 7406075729478,29921472956312,121154164282920, 491604207872268] |