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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 30 |
| 4 | 348 |
| 5 | 3956 |
| 6 | 44916 |
| 7 | 509978 |
| 8 | 5790456 |
| 9 | 65747178 |
| 10 | 746521190 |
| 11 | 8476319172 |
| 12 | 96243740012 |
| 13 | 1092792451740 |
| 14 | 12408031373682 |
| 15 | 140886078048560 |
| 16 | 1599680593324818 |
| 17 | 18163455439700846 |
| 18 | 206235616589902956 |
[0,2,30,348,3956,44916,509978,5790456,65747178, 746521190,8476319172,96243740012,1092792451740, 12408031373682,140886078048560,1599680593324818, 18163455439700846,206235616589902956] |