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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 28 |
| 3 | 408 |
| 4 | 7896 |
| 5 | 137555 |
| 6 | 2496144 |
| 7 | 44599477 |
| 8 | 801617712 |
| 9 | 14375440584 |
| 10 | 258018516140 |
| 11 | 4629531440711 |
| 12 | 83076469908768 |
| 13 | 1490726895438793 |
| 14 | 26750144944686436 |
| 15 | 480010941060482040 |
| 16 | 8613453244178393184 |
| 17 | 154562103244937408987 |
| 18 | 2773504708179098411952 |
[1,28,408,7896,137555,2496144,44599477,801617712, 14375440584,258018516140,4629531440711, 83076469908768,1490726895438793,26750144944686436, 480010941060482040,8613453244178393184, 154562103244937408987,2773504708179098411952] |