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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 68 |
| 5 | 246 |
| 6 | 905 |
| 7 | 3364 |
| 8 | 12624 |
| 9 | 47715 |
| 10 | 181392 |
| 11 | 692808 |
| 12 | 2656441 |
| 13 | 10219208 |
| 14 | 39423792 |
| 15 | 152461079 |
| 16 | 590861182 |
| 17 | 2294182428 |
| 18 | 8922674221 |
| 19 | 34754402618 |
| 20 | 135552346392 |
| 21 | 529335200219 |
| 22 | 2069344561102 |
| 23 | 8097878381208 |
| 24 | 31718268482881 |
| 25 | 124341261876650 |
[1,2,6,19,68,246,905,3364,12624,47715,181392, 692808,2656441,10219208,39423792,152461079, 590861182,2294182428,8922674221,34754402618, 135552346392,529335200219,2069344561102, 8097878381208,31718268482881,124341261876650] |