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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 48 |
| 4 | 261 |
| 5 | 1470 |
| 6 | 8619 |
| 7 | 51816 |
| 8 | 318155 |
| 9 | 1985630 |
| 10 | 12561308 |
| 11 | 80360280 |
| 12 | 519013571 |
| 13 | 3379514970 |
| 14 | 22161470850 |
| 15 | 146227235904 |
| 16 | 970126550763 |
| 17 | 6467496499590 |
| 18 | 43304243215638 |
| 19 | 291087137589552 |
| 20 | 1963598081845335 |
| 21 | 13288619577124122 |
| 22 | 90195242361688863 |
| 23 | 613843707553183800 |
[1,2,10,48,261,1470,8619,51816,318155,1985630, 12561308,80360280,519013571,3379514970, 22161470850,146227235904,970126550763, 6467496499590,43304243215638,291087137589552, 1963598081845335,13288619577124122, 90195242361688863,613843707553183800] |