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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 30 |
| 3 | 150 |
| 4 | 750 |
| 5 | 3750 |
| 6 | 18750 |
| 7 | 93750 |
| 8 | 468735 |
| 9 | 2343600 |
| 10 | 11717640 |
| 11 | 58586400 |
| 12 | 292923000 |
| 13 | 1464570000 |
| 14 | 7322625000 |
| 15 | 36612000000 |
| 16 | 183054375210 |
| 17 | 915243753000 |
| 18 | 4576078154040 |
| 19 | 22879687737000 |
| 20 | 114394923627000 |
| 21 | 571957043385000 |
[1,6,30,150,750,3750,18750,93750,468735,2343600, 11717640,58586400,292923000,1464570000,7322625000, 36612000000,183054375210,915243753000, 4576078154040,22879687737000,114394923627000, 571957043385000] |