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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 27 |
| 2 | 351 |
| 3 | 3003 |
| 4 | 19305 |
| 5 | 100386 |
| 6 | 442442 |
| 7 | 1706562 |
| 8 | 5895396 |
| 9 | 18559580 |
| 10 | 53965548 |
| 11 | 146477916 |
| 12 | 374332452 |
| 13 | 907036326 |
| 14 | 2096092350 |
| 15 | 4642456390 |
| 16 | 9895762305 |
| 17 | 20373628275 |
| 18 | 40639459575 |
| 19 | 78751105875 |
| 20 | 148599912825 |
| 21 | 273612537900 |
| 22 | 492502568220 |
| 23 | 868056366060 |
| 24 | 1500344336400 |
[1,27,351,3003,19305,100386,442442,1706562, 5895396,18559580,53965548,146477916,374332452, 907036326,2096092350,4642456390,9895762305, 20373628275,40639459575,78751105875,148599912825, 273612537900,492502568220,868056366060, 1500344336400] |