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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 24 |
| 4 | 165 |
| 5 | 1560 |
| 6 | 19684 |
| 7 | 299600 |
| 8 | 5381685 |
| 9 | 111111340 |
| 10 | 2593758618 |
| 11 | 67546215528 |
| 12 | 1941507500933 |
| 13 | 61054982558024 |
| 14 | 2085209014017960 |
| 15 | 76861433640597376 |
| 16 | 3041324492665174641 |
| 17 | 128583032925805678368 |
| 18 | 5784852794346334629910 |
| 19 | 275941052631578947368440 |
[1,2,6,24,165,1560,19684,299600,5381685,111111340, 2593758618,67546215528,1941507500933, 61054982558024,2085209014017960,76861433640597376, 3041324492665174641,128583032925805678368, 5784852794346334629910,275941052631578947368440] |