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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 40 |
| 4 | 198 |
| 5 | 912 |
| 6 | 4540 |
| 7 | 22032 |
| 8 | 110598 |
| 9 | 550240 |
| 10 | 2783220 |
| 11 | 14041104 |
| 12 | 71469468 |
| 13 | 363722912 |
| 14 | 1860732856 |
| 15 | 9526388000 |
| 16 | 48933655494 |
| 17 | 251617706688 |
| 18 | 1296741709252 |
| 19 | 6690068720016 |
| 20 | 34571534145588 |
| 21 | 178829630116896 |
| 22 | 926198946642760 |
| 23 | 4801277360678240 |
| 24 | 24913966227624604 |
[1,2,10,40,198,912,4540,22032,110598,550240, 2783220,14041104,71469468,363722912,1860732856, 9526388000,48933655494,251617706688,1296741709252, 6690068720016,34571534145588,178829630116896, 926198946642760,4801277360678240, 24913966227624604] |