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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 72 |
| 5 | 672 |
| 6 | 7640 |
| 7 | 102072 |
| 8 | 1564864 |
| 9 | 27064448 |
| 10 | 521248320 |
| 11 | 11064781760 |
| 12 | 256702399360 |
| 13 | 6462978471168 |
| 14 | 175520877380992 |
| 15 | 5115062135795584 |
| 16 | 159227683153536000 |
| 17 | 5273353734210310144 |
| 18 | 185143079148664099840 |
| 19 | 6869062513111759635456 |
[1,1,2,10,72,672,7640,102072,1564864,27064448, 521248320,11064781760,256702399360,6462978471168, 175520877380992,5115062135795584, 159227683153536000,5273353734210310144, 185143079148664099840,6869062513111759635456] |