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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 69 |
| 6 | 552 |
| 7 | 5901 |
| 8 | 81444 |
| 9 | 1411197 |
| 10 | 30006624 |
| 11 | 768410349 |
| 12 | 23329316316 |
| 13 | 828656935485 |
| 14 | 34046249891736 |
| 15 | 1602162894386157 |
| 16 | 85614553733396628 |
| 17 | 5155811948641383933 |
| 18 | 347560275319797255888 |
| 19 | 26069526814633439369325 |
[0,1,3,12,69,552,5901,81444,1411197,30006624, 768410349,23329316316,828656935485,34046249891736, 1602162894386157,85614553733396628, 5155811948641383933,347560275319797255888, 26069526814633439369325] |