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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 31 |
| 5 | 91 |
| 6 | 274 |
| 7 | 820 |
| 8 | 2461 |
| 9 | 7381 |
| 10 | 22144 |
| 11 | 66430 |
| 12 | 199291 |
| 13 | 597871 |
| 14 | 1793614 |
| 15 | 5380840 |
| 16 | 16142521 |
| 17 | 48427561 |
| 18 | 145282684 |
| 19 | 435848050 |
| 20 | 1307544151 |
| 21 | 3922632451 |
| 22 | 11767897354 |
| 23 | 35303692060 |
| 24 | 105911076181 |
| 25 | 317733228541 |
| 26 | 953199685624 |
| 27 | 2859599056870 |
| 28 | 8578797170611 |
[1,1,4,10,31,91,274,820,2461,7381,22144,66430, 199291,597871,1793614,5380840,16142521,48427561, 145282684,435848050,1307544151,3922632451, 11767897354,35303692060,105911076181,317733228541, 953199685624,2859599056870,8578797170611] |