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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 9 |
| 2 | 40 |
| 3 | 178 |
| 4 | 792 |
| 5 | 3524 |
| 6 | 15680 |
| 7 | 69768 |
| 8 | 310432 |
| 9 | 1381264 |
| 10 | 6145920 |
| 11 | 27346208 |
| 12 | 121676672 |
| 13 | 541399104 |
| 14 | 2408949760 |
| 15 | 10718597248 |
| 16 | 47692288512 |
| 17 | 212206348544 |
| 18 | 944209971200 |
| 19 | 4201252581888 |
| 20 | 18693430269952 |
| 21 | 83176226243584 |
| 22 | 370091765514240 |
| 23 | 1646719514544128 |
[2,9,40,178,792,3524,15680,69768,310432,1381264, 6145920,27346208,121676672,541399104,2408949760, 10718597248,47692288512,212206348544,944209971200, 4201252581888,18693430269952,83176226243584, 370091765514240,1646719514544128] |