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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 12 |
| 3 | 18 |
| 4 | 62 |
| 5 | 420 |
| 6 | 682 |
| 7 | 5828 |
| 8 | 16852 |
| 9 | 61952 |
| 10 | 201184 |
| 11 | 669920 |
| 12 | 2184064 |
| 13 | 7126784 |
| 14 | 23147776 |
| 15 | 75118592 |
| 16 | 243460096 |
| 17 | 788658176 |
| 18 | 2553683968 |
| 19 | 8267055104 |
| 20 | 26758955008 |
| 21 | 86606348288 |
| 22 | 280288952320 |
| 23 | 907084169216 |
| 24 | 2935485890560 |
[1,2,12,18,62,420,682,5828,16852,61952,201184, 669920,2184064,7126784,23147776,75118592, 243460096,788658176,2553683968,8267055104, 26758955008,86606348288,280288952320,907084169216, 2935485890560] |