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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 9 |
| 4 | 36 |
| 5 | 140 |
| 6 | 540 |
| 7 | 2142 |
| 8 | 8624 |
| 9 | 35856 |
| 10 | 152280 |
| 11 | 666380 |
| 12 | 2982672 |
| 13 | 13716144 |
| 14 | 64487696 |
| 15 | 310693320 |
| 16 | 1528801920 |
| 17 | 7691652992 |
| 18 | 39474925344 |
| 19 | 206758346256 |
| 20 | 1103332900160 |
| 21 | 5999356762560 |
| 22 | 33197323465152 |
| 23 | 186925844947424 |
| 24 | 1069977071943936 |
[2,9,36,140,540,2142,8624,35856,152280,666380, 2982672,13716144,64487696,310693320,1528801920, 7691652992,39474925344,206758346256,1103332900160, 5999356762560,33197323465152,186925844947424, 1069977071943936] |