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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 56 |
| 4 | 631 |
| 5 | 15457 |
| 6 | 582374 |
| 7 | 18589286 |
| 8 | 894499204 |
| 9 | 51154344582 |
| 10 | 3823359163826 |
| 11 | 274722100927166 |
| 12 | 25458967562911128 |
| 13 | 2569179797929092506 |
| 14 | 284554990016509385086 |
| 15 | 37830153187190688287522 |
| 16 | 5093072752898942262610007 |
| 17 | 798814778335473578083666573 |
[1,1,4,56,631,15457,582374,18589286,894499204, 51154344582,3823359163826,274722100927166, 25458967562911128,2569179797929092506, 284554990016509385086,37830153187190688287522, 5093072752898942262610007, 798814778335473578083666573] |