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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 27 |
| 4 | 218 |
| 5 | 2178 |
| 6 | 25529 |
| 7 | 343392 |
| 8 | 5205948 |
| 9 | 87740878 |
| 10 | 1626182463 |
| 11 | 32852520594 |
| 12 | 718169744206 |
| 13 | 16883948532684 |
| 14 | 424649281630018 |
| 15 | 11374387591643065 |
| 16 | 323183885622356184 |
| 17 | 9706973096869527210 |
| 18 | 307248234238900686688 |
| 19 | 10220414166250239718518 |
[1,1,4,27,218,2178,25529,343392,5205948,87740878, 1626182463,32852520594,718169744206, 16883948532684,424649281630018,11374387591643065, 323183885622356184,9706973096869527210, 307248234238900686688,10220414166250239718518] |