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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 81 |
| 3 | 1875 |
| 4 | 14406 |
| 5 | 219615 |
| 6 | 599781 |
| 7 | 3006756 |
| 8 | 5864445 |
| 9 | 18469506 |
| 10 | 74264505 |
| 11 | 110822520 |
| 12 | 320481531 |
| 13 | 593409810 |
| 14 | 789743031 |
| 15 | 1346791956 |
| 16 | 2769558831 |
| 17 | 5271052035 |
| 18 | 6438316065 |
| 19 | 11304778881 |
| 20 | 16009359030 |
| 21 | 18913228506 |
| 22 | 30381063180 |
[6,81,1875,14406,219615,599781,3006756,5864445, 18469506,74264505,110822520,320481531,593409810, 789743031,1346791956,2769558831,5271052035, 6438316065,11304778881,16009359030,18913228506, 30381063180] |