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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 74 |
| 4 | 603 |
| 5 | 4909 |
| 6 | 39960 |
| 7 | 325277 |
| 8 | 2647773 |
| 9 | 21553018 |
| 10 | 175442751 |
| 11 | 1428113633 |
| 12 | 11624923440 |
| 13 | 94627515529 |
| 14 | 770273175681 |
| 15 | 6270065972426 |
| 16 | 51038681522067 |
| 17 | 415457671891621 |
| 18 | 3381848276370120 |
| 19 | 27528430784089733 |
| 20 | 224082939122216757 |
| 21 | 1824047436611322682 |
[0,1,9,74,603,4909,39960,325277,2647773,21553018, 175442751,1428113633,11624923440,94627515529, 770273175681,6270065972426,51038681522067, 415457671891621,3381848276370120, 27528430784089733,224082939122216757, 1824047436611322682] |