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| n | a(n) |
|---|---|
| 1 | 81 |
| 2 | 540 |
| 3 | 3640 |
| 4 | 24208 |
| 5 | 162016 |
| 6 | 1081504 |
| 7 | 7227096 |
| 8 | 48272160 |
| 9 | 322493040 |
| 10 | 2154281664 |
| 11 | 14391427080 |
| 12 | 96138251504 |
| 13 | 642233318880 |
| 14 | 4290297708128 |
| 15 | 28660448653048 |
| 16 | 191460012669504 |
| 17 | 1279008408531440 |
| 18 | 8544145042353728 |
| 19 | 57077359575083624 |
[81,540,3640,24208,162016,1081504,7227096, 48272160,322493040,2154281664,14391427080, 96138251504,642233318880,4290297708128, 28660448653048,191460012669504,1279008408531440, 8544145042353728,57077359575083624] |