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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 48 |
| 4 | 286 |
| 5 | 1842 |
| 6 | 12486 |
| 7 | 87811 |
| 8 | 634847 |
| 9 | 4688676 |
| 10 | 35221832 |
| 11 | 268282855 |
| 12 | 2067174645 |
| 13 | 16083734329 |
| 14 | 126186554308 |
| 15 | 997171512998 |
| 16 | 7929819784355 |
| 17 | 63411730258053 |
| 18 | 509588049810620 |
| 19 | 4113254119923150 |
| 20 | 33333125878283632 |
| 21 | 271097737169671824 |
| 22 | 2212039245722726118 |
[1,2,9,48,286,1842,12486,87811,634847,4688676, 35221832,268282855,2067174645,16083734329, 126186554308,997171512998,7929819784355, 63411730258053,509588049810620,4113254119923150, 33333125878283632,271097737169671824, 2212039245722726118] |