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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 15 |
| 4 | 62 |
| 5 | 262 |
| 6 | 1148 |
| 7 | 5123 |
| 8 | 23316 |
| 9 | 107570 |
| 10 | 502664 |
| 11 | 2372786 |
| 12 | 11302858 |
| 13 | 54256236 |
| 14 | 262226900 |
| 15 | 1274944859 |
| 16 | 6231845040 |
| 17 | 30605344282 |
| 18 | 150948390672 |
| 19 | 747356368322 |
| 20 | 3713140528364 |
| 21 | 18506907541124 |
| 22 | 92509837573736 |
| 23 | 463660345091686 |
[1,1,4,15,62,262,1148,5123,23316,107570,502664, 2372786,11302858,54256236,262226900,1274944859, 6231845040,30605344282,150948390672,747356368322, 3713140528364,18506907541124,92509837573736, 463660345091686] |