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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 35 |
| 5 | 226 |
| 6 | 1787 |
| 7 | 16717 |
| 8 | 180560 |
| 9 | 2211181 |
| 10 | 30273047 |
| 11 | 458186752 |
| 12 | 7596317885 |
| 13 | 136907048461 |
| 14 | 2665084902482 |
| 15 | 55726440112987 |
| 16 | 1245661569161135 |
| 17 | 29642264728189066 |
| 18 | 748158516941653967 |
| 19 | 19962900431638852297 |
| 20 | 561472467839585937560 |
| 21 | 16602088291822017588121 |
[1,1,2,7,35,226,1787,16717,180560,2211181, 30273047,458186752,7596317885,136907048461, 2665084902482,55726440112987,1245661569161135, 29642264728189066,748158516941653967, 19962900431638852297,561472467839585937560, 16602088291822017588121] |