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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 39 |
| 3 | 616 |
| 4 | 13445 |
| 5 | 374976 |
| 6 | 12738523 |
| 7 | 510366592 |
| 8 | 23561390889 |
| 9 | 1231594508800 |
| 10 | 71902556218031 |
| 11 | 4637321353737216 |
| 12 | 327439395476545261 |
| 13 | 25123251004703358976 |
| 14 | 2081326422827575699875 |
[1,4,39,616,13445,374976,12738523,510366592, 23561390889,1231594508800,71902556218031, 4637321353737216,327439395476545261, 25123251004703358976,2081326422827575699875] |