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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 12 |
| 4 | 151 |
| 5 | 2180 |
| 6 | 36261 |
| 7 | 688408 |
| 8 | 14750191 |
| 9 | 352961064 |
| 10 | 9345270925 |
| 11 | 271562360036 |
| 12 | 8599866305031 |
| 13 | 294969253011628 |
| 14 | 10898548778881141 |
| 15 | 431703607027230000 |
| 16 | 18254845289747040991 |
| 17 | 820907602015573913552 |
| 18 | 39124764979819837803549 |
| 19 | 1970218861127675697564604 |
[0,1,12,151,2180,36261,688408,14750191,352961064, 9345270925,271562360036,8599866305031, 294969253011628,10898548778881141, 431703607027230000,18254845289747040991, 820907602015573913552,39124764979819837803549, 1970218861127675697564604] |