The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 12 |
| 3 | 80 |
| 4 | 552 |
| 5 | 3912 |
| 6 | 28224 |
| 7 | 206208 |
| 8 | 1520784 |
| 9 | 11297546 |
| 10 | 84413912 |
| 11 | 633713808 |
| 12 | 4776117216 |
| 13 | 36115518376 |
| 14 | 273868321536 |
| 15 | 2081866609920 |
| 16 | 15859616674336 |
| 17 | 121046064563376 |
| 18 | 925411686479820 |
| 19 | 7085465166635440 |
| 20 | 54323193841192752 |
| 21 | 416993869451825424 |
| 22 | 3204447137019290944 |
[1,2,12,80,552,3912,28224,206208,1520784,11297546, 84413912,633713808,4776117216,36115518376, 273868321536,2081866609920,15859616674336, 121046064563376,925411686479820,7085465166635440, 54323193841192752,416993869451825424, 3204447137019290944] |