| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 16 |
| 6 | 144 |
| 7 | 7056 |
| 8 | 13046544 |
| 9 | 42600214749456 |
| 10 | 453694852221644777216198544 |
| 11 | 51459754733114686962148583539748993964925660496781456 |
[1,1,1,4,16,144,7056,13046544,42600214749456, 453694852221644777216198544, 51459754733114686962148583539748993964925660496781\ 456] |