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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 27 |
| 6 | 81 |
| 7 | 262 |
| 8 | 910 |
| 9 | 3363 |
| 10 | 13150 |
| 11 | 54135 |
| 12 | 233671 |
| 13 | 1053911 |
| 14 | 4951997 |
| 15 | 24177536 |
| 16 | 122381035 |
| 17 | 640937746 |
| 18 | 3466900453 |
| 19 | 19337255086 |
| 20 | 111057640382 |
| 21 | 655892813805 |
| 22 | 3978591077096 |
| 23 | 24760700544301 |
| 24 | 157941950878839 |
[1,1,2,4,10,27,81,262,910,3363,13150,54135,233671, 1053911,4951997,24177536,122381035,640937746, 3466900453,19337255086,111057640382,655892813805, 3978591077096,24760700544301,157941950878839] |