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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 32 |
| 3 | 162 |
| 4 | 800 |
| 5 | 3906 |
| 6 | 18992 |
| 7 | 92322 |
| 8 | 449600 |
| 9 | 2195586 |
| 10 | 10755152 |
| 11 | 52845282 |
| 12 | 260386400 |
| 13 | 1286217666 |
| 14 | 6367168112 |
| 15 | 31576971042 |
| 16 | 156839811200 |
| 17 | 779990182146 |
| 18 | 3883029321872 |
| 19 | 19347201973602 |
| 20 | 96463456484000 |
| 21 | 481224744361026 |
[1,6,32,162,800,3906,18992,92322,449600,2195586, 10755152,52845282,260386400,1286217666,6367168112, 31576971042,156839811200,779990182146, 3883029321872,19347201973602,96463456484000, 481224744361026] |