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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 6 |
| 3 | 9 |
| 4 | 54 |
| 5 | 54 |
| 6 | 540 |
| 7 | 405 |
| 8 | 5670 |
| 9 | 3402 |
| 10 | 61236 |
| 11 | 30618 |
| 12 | 673596 |
| 13 | 288684 |
| 14 | 7505784 |
| 15 | 2814669 |
| 16 | 84440070 |
| 17 | 28146690 |
| 18 | 956987460 |
| 19 | 287096238 |
| 20 | 10909657044 |
| 21 | 2975361012 |
| 22 | 124965162504 |
| 23 | 31241290626 |
| 24 | 1437099368796 |
| 25 | 331638315876 |
| 26 | 16581915793800 |
[1,3,6,9,54,54,540,405,5670,3402,61236,30618, 673596,288684,7505784,2814669,84440070,28146690, 956987460,287096238,10909657044,2975361012, 124965162504,31241290626,1437099368796, 331638315876,16581915793800] |