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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 75 |
| 4 | 1464 |
| 5 | 39065 |
| 6 | 1324080 |
| 7 | 54460987 |
| 8 | 2635269504 |
| 9 | 146681897553 |
| 10 | 9233067686400 |
| 11 | 648538095601451 |
| 12 | 50289434320131072 |
| 13 | 4267083467872455529 |
| 14 | 393266542856236148736 |
| 15 | 39121731305087283953115 |
| 16 | 4178124995723585643970560 |
| 17 | 476806534212831941528989217 |
| 18 | 57905078072597558361906610176 |
[1,1,6,75,1464,39065,1324080,54460987,2635269504, 146681897553,9233067686400,648538095601451, 50289434320131072,4267083467872455529, 393266542856236148736,39121731305087283953115, 4178124995723585643970560, 476806534212831941528989217, 57905078072597558361906610176] |