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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 66 |
| 5 | 449 |
| 6 | 3678 |
| 7 | 35111 |
| 8 | 383192 |
| 9 | 4704300 |
| 10 | 64172052 |
| 11 | 962908056 |
| 12 | 15762088585 |
| 13 | 279514500434 |
| 14 | 5338014558032 |
| 15 | 109224066408835 |
| 16 | 2383887010044728 |
| 17 | 55281768382909480 |
| 18 | 1357381019671809552 |
| 19 | 35180557115610914376 |
| 20 | 959798458208463538416 |
| 21 | 27494554196938752676656 |
[1,1,3,12,66,449,3678,35111,383192,4704300, 64172052,962908056,15762088585,279514500434, 5338014558032,109224066408835,2383887010044728, 55281768382909480,1357381019671809552, 35180557115610914376,959798458208463538416, 27494554196938752676656] |