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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 61 |
| 5 | 261 |
| 6 | 3991 |
| 7 | 24403 |
| 8 | 524217 |
| 9 | 4149001 |
| 10 | 114544171 |
| 11 | 1111976031 |
| 12 | 37492210933 |
| 13 | 431097055117 |
| 14 | 17165526306111 |
| 15 | 228085258466731 |
| 16 | 10472666396599921 |
| 17 | 157882659583461393 |
| 18 | 8211536252680154707 |
| 19 | 138474928851961700791 |
| 20 | 8045878340298511456941 |
[1,1,3,7,61,261,3991,24403,524217,4149001, 114544171,1111976031,37492210933,431097055117, 17165526306111,228085258466731,10472666396599921, 157882659583461393,8211536252680154707, 138474928851961700791,8045878340298511456941] |