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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 45 |
| 5 | 241 |
| 6 | 1525 |
| 7 | 11096 |
| 8 | 91441 |
| 9 | 842185 |
| 10 | 8577871 |
| 11 | 95768454 |
| 12 | 1163339221 |
| 13 | 15278140593 |
| 14 | 215739927481 |
| 15 | 3259925357716 |
| 16 | 52489756856993 |
| 17 | 897249441166993 |
| 18 | 16228613753092315 |
| 19 | 309660835748163394 |
| 20 | 6216734677256575581 |
| 21 | 130994769191324727697 |
[1,1,3,10,45,241,1525,11096,91441,842185,8577871, 95768454,1163339221,15278140593,215739927481, 3259925357716,52489756856993,897249441166993, 16228613753092315,309660835748163394, 6216734677256575581,130994769191324727697] |