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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 12 |
| 2 | 90 |
| 3 | 560 |
| 4 | 3150 |
| 5 | 16632 |
| 6 | 84084 |
| 7 | 411840 |
| 8 | 1969110 |
| 9 | 9237800 |
| 10 | 42678636 |
| 11 | 194699232 |
| 12 | 878850700 |
| 13 | 3931426800 |
| 14 | 17450721000 |
| 15 | 76938289920 |
| 16 | 337206098790 |
| 17 | 1470171918600 |
| 18 | 6379820115900 |
| 19 | 27569305764000 |
| 20 | 118685861314020 |
| 21 | 509191949220240 |
| 22 | 2177742427450200 |
| 23 | 9287309860732800 |
[1,12,90,560,3150,16632,84084,411840,1969110, 9237800,42678636,194699232,878850700,3931426800, 17450721000,76938289920,337206098790, 1470171918600,6379820115900,27569305764000, 118685861314020,509191949220240,2177742427450200, 9287309860732800] |