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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 10 |
| 5 | 26 |
| 6 | 91 |
| 7 | 260 |
| 8 | 820 |
| 9 | 2420 |
| 10 | 7381 |
| 11 | 22022 |
| 12 | 66430 |
| 13 | 198926 |
| 14 | 597871 |
| 15 | 1792520 |
| 16 | 5380840 |
| 17 | 16139240 |
| 18 | 48427561 |
| 19 | 145272842 |
| 20 | 435848050 |
| 21 | 1307514626 |
| 22 | 3922632451 |
| 23 | 11767808780 |
| 24 | 35303692060 |
| 25 | 105910810460 |
| 26 | 317733228541 |
| 27 | 953198888462 |
[0,0,1,2,10,26,91,260,820,2420,7381,22022,66430, 198926,597871,1792520,5380840,16139240,48427561, 145272842,435848050,1307514626,3922632451, 11767808780,35303692060,105910810460,317733228541, 953198888462] |