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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 6 |
| 5 | 21 |
| 6 | 76 |
| 7 | 276 |
| 8 | 1001 |
| 9 | 3631 |
| 10 | 13171 |
| 11 | 47776 |
| 12 | 173301 |
| 13 | 628626 |
| 14 | 2280256 |
| 15 | 8271321 |
| 16 | 30003101 |
| 17 | 108832201 |
| 18 | 394774126 |
| 19 | 1431989881 |
| 20 | 5194350096 |
| 21 | 18841804176 |
| 22 | 68346102601 |
| 23 | 247916266251 |
| 24 | 899282808131 |
| 25 | 3262027059496 |
| 26 | 11832563061001 |
[1,1,1,6,21,76,276,1001,3631,13171,47776,173301, 628626,2280256,8271321,30003101,108832201, 394774126,1431989881,5194350096,18841804176, 68346102601,247916266251,899282808131, 3262027059496,11832563061001] |