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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 42 |
| 5 | 262 |
| 6 | 1828 |
| 7 | 13820 |
| 8 | 110954 |
| 9 | 933458 |
| 10 | 8152860 |
| 11 | 73424650 |
| 12 | 678390116 |
| 13 | 6405031050 |
| 14 | 61606881612 |
| 15 | 602188541928 |
| 16 | 5969806669034 |
| 17 | 59923200729046 |
| 18 | 608188709574124 |
| 19 | 6234277838531806 |
| 20 | 64477712119584604 |
| 21 | 672265814872772972 |
| 22 | 7060941974458061392 |
[1,1,2,8,42,262,1828,13820,110954,933458,8152860, 73424650,678390116,6405031050,61606881612, 602188541928,5969806669034,59923200729046, 608188709574124,6234277838531806, 64477712119584604,672265814872772972, 7060941974458061392] |