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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 7 |
| 4 | 21 |
| 5 | 76 |
| 6 | 276 |
| 7 | 1348 |
| 8 | 8261 |
| 9 | 57523 |
| 10 | 494123 |
| 11 | 5241083 |
| 12 | 66302797 |
| 13 | 1017030742 |
| 14 | 19028971842 |
| 15 | 430245073504 |
| 16 | 11780079516040 |
| 17 | 391601126619884 |
| 18 | 15773508409281591 |
| 19 | 769806377138722292 |
| 20 | 45555272775339596310 |
[1,2,4,7,21,76,276,1348,8261,57523,494123,5241083, 66302797,1017030742,19028971842,430245073504, 11780079516040,391601126619884,15773508409281591, 769806377138722292,45555272775339596310] |