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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 225 |
| 4 | 4410 |
| 5 | 105903 |
| 6 | 2746098 |
| 7 | 73140525 |
| 8 | 1965803130 |
| 9 | 52995903003 |
| 10 | 1430162760978 |
| 11 | 38607856205625 |
| 12 | 1042353276205050 |
| 13 | 28143008896575303 |
| 14 | 759856474192364658 |
| 15 | 20516081909157771525 |
| 16 | 553933825501236490170 |
| 17 | 14956209814120079146803 |
| 18 | 403817633711525094117138 |
[1,3,18,225,4410,105903,2746098,73140525, 1965803130,52995903003,1430162760978, 38607856205625,1042353276205050,28143008896575303, 759856474192364658,20516081909157771525, 553933825501236490170,14956209814120079146803, 403817633711525094117138] |