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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 16 |
| 5 | 89 |
| 6 | 579 |
| 7 | 3989 |
| 8 | 28630 |
| 9 | 210865 |
| 10 | 1584308 |
| 11 | 12091902 |
| 12 | 93483120 |
| 13 | 730503054 |
| 14 | 5760438853 |
| 15 | 45780146521 |
| 16 | 366304396662 |
| 17 | 2948412461685 |
| 18 | 23857049238752 |
| 19 | 193944769559906 |
| 20 | 1583294537879106 |
| 21 | 12974430494985262 |
| 22 | 106685110047676402 |
[1,2,4,16,89,579,3989,28630,210865,1584308, 12091902,93483120,730503054,5760438853, 45780146521,366304396662,2948412461685, 23857049238752,193944769559906,1583294537879106, 12974430494985262,106685110047676402] |