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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 10 |
| 3 | 38 |
| 4 | 148 |
| 5 | 620 |
| 6 | 2600 |
| 7 | 11480 |
| 8 | 50256 |
| 9 | 229296 |
| 10 | 1032352 |
| 11 | 4816736 |
| 12 | 22118720 |
| 13 | 104890048 |
| 14 | 488768128 |
| 15 | 2346515840 |
| 16 | 11058545920 |
| 17 | 53605825280 |
| 18 | 254908828160 |
| 19 | 1245304583680 |
| 20 | 5965139153920 |
| 21 | 29328419056640 |
| 22 | 141339991746560 |
[1,3,10,38,148,620,2600,11480,50256,229296, 1032352,4816736,22118720,104890048,488768128, 2346515840,11058545920,53605825280,254908828160, 1245304583680,5965139153920,29328419056640, 141339991746560] |