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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 28 |
| 4 | 136 |
| 5 | 656 |
| 6 | 3168 |
| 7 | 15296 |
| 8 | 73856 |
| 9 | 356608 |
| 10 | 1721856 |
| 11 | 8313856 |
| 12 | 40142848 |
| 13 | 193826816 |
| 14 | 935878656 |
| 15 | 4518821888 |
| 16 | 21818802176 |
| 17 | 105350496256 |
| 18 | 508677193728 |
| 19 | 2456110759936 |
| 20 | 11859151814656 |
| 21 | 57261050298368 |
| 22 | 276480808452096 |
[0,1,6,28,136,656,3168,15296,73856,356608,1721856, 8313856,40142848,193826816,935878656,4518821888, 21818802176,105350496256,508677193728, 2456110759936,11859151814656,57261050298368, 276480808452096] |