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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 8 |
| 3 | 102 |
| 4 | 1712 |
| 5 | 34785 |
| 6 | 819384 |
| 7 | 21810124 |
| 8 | 645122272 |
| 9 | 20957720148 |
| 10 | 741260263600 |
| 11 | 28350052179438 |
| 12 | 1165931175542064 |
| 13 | 51320048879474206 |
| 14 | 2407857124657086480 |
| 15 | 119990501174741855400 |
| 16 | 6330579163195128292800 |
| 17 | 352584892981590315935084 |
| 18 | 20675941712941698695206368 |
| 19 | 1273517057922072215818491064 |
| 20 | 82210136955409063394289646720 |
[1,1,8,102,1712,34785,819384,21810124,645122272, 20957720148,741260263600,28350052179438, 1165931175542064,51320048879474206, 2407857124657086480,119990501174741855400, 6330579163195128292800,352584892981590315935084, 20675941712941698695206368, 1273517057922072215818491064, 82210136955409063394289646720] |