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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 38 |
| 5 | 210 |
| 6 | 1314 |
| 7 | 8358 |
| 8 | 55118 |
| 9 | 370842 |
| 10 | 2541626 |
| 11 | 17668926 |
| 12 | 124321750 |
| 13 | 883614498 |
| 14 | 6334772562 |
| 15 | 45754956054 |
| 16 | 332639032734 |
| 17 | 2432189656362 |
| 18 | 17874332863722 |
| 19 | 131957567836206 |
| 20 | 978161729926950 |
| 21 | 7277592773408562 |
| 22 | 54327287358246018 |
| 23 | 406792963221032454 |
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