| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 17 |
| 4 | 144 |
| 5 | 1634 |
| 6 | 23312 |
| 7 | 401274 |
| 8 | 8096680 |
| 9 | 187472136 |
| 10 | 4900535832 |
| 11 | 142766286552 |
| 12 | 4587190461840 |
| 13 | 161161214978880 |
| 14 | 6146415080939520 |
| 15 | 252902928346825104 |
| 16 | 11167368115492742400 |
| 17 | 526752556713346955520 |
| 18 | 26433830208985721222400 |
| 19 | 1406218428780691953635712 |
[1,1,3,17,144,1634,23312,401274,8096680,187472136, 4900535832,142766286552,4587190461840, 161161214978880,6146415080939520, 252902928346825104,11167368115492742400, 526752556713346955520,26433830208985721222400, 1406218428780691953635712] |