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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 34 |
| 3 | 328 |
| 4 | 3334 |
| 5 | 34904 |
| 6 | 372436 |
| 7 | 4027216 |
| 8 | 43976774 |
| 9 | 483860632 |
| 10 | 5355697084 |
| 11 | 59569288816 |
| 12 | 665238165916 |
| 13 | 7454247891952 |
| 14 | 83769667651816 |
| 15 | 943744775565728 |
| 16 | 10655369806377542 |
| 17 | 120535523282756632 |
| 18 | 1365840013196530348 |
| 19 | 15500428304345011504 |
| 20 | 176148760580561346484 |
[1,4,34,328,3334,34904,372436,4027216,43976774, 483860632,5355697084,59569288816,665238165916, 7454247891952,83769667651816,943744775565728, 10655369806377542,120535523282756632, 1365840013196530348,15500428304345011504, 176148760580561346484] |