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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 55 |
| 5 | 400 |
| 6 | 3266 |
| 7 | 28999 |
| 8 | 274537 |
| 9 | 2734885 |
| 10 | 28401315 |
| 11 | 305352146 |
| 12 | 3380956839 |
| 13 | 38394091370 |
| 14 | 445702108969 |
| 15 | 5274935433915 |
| 16 | 63507021523471 |
| 17 | 776347636736261 |
| 18 | 9621502184089320 |
| 19 | 120726786082609207 |
| 20 | 1531938384684090884 |
| 21 | 19639252409244653785 |
| 22 | 254143269904958943103 |
| 23 | 3317204158078663935592 |
[1,1,2,9,55,400,3266,28999,274537,2734885, 28401315,305352146,3380956839,38394091370, 445702108969,5274935433915,63507021523471, 776347636736261,9621502184089320, 120726786082609207,1531938384684090884, 19639252409244653785,254143269904958943103, 3317204158078663935592] |