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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 10 |
| 6 | 26 |
| 7 | 72 |
| 8 | 205 |
| 9 | 600 |
| 10 | 1790 |
| 11 | 5428 |
| 12 | 16676 |
| 13 | 51800 |
| 14 | 162408 |
| 15 | 513288 |
| 16 | 1633543 |
| 17 | 5230506 |
| 18 | 16838080 |
| 19 | 54465356 |
| 20 | 176933606 |
| 21 | 577002976 |
| 22 | 1888274740 |
| 23 | 6199187904 |
| 24 | 20411160754 |
| 25 | 67384417204 |
| 26 | 223006818992 |
| 27 | 739711312416 |
| 28 | 2458778309456 |
[1,1,2,4,10,26,72,205,600,1790,5428,16676,51800, 162408,513288,1633543,5230506,16838080,54465356, 176933606,577002976,1888274740,6199187904, 20411160754,67384417204,223006818992,739711312416, 2458778309456] |