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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 7 |
| 5 | 76 |
| 6 | 164 |
| 7 | 1679 |
| 8 | 3611 |
| 9 | 36872 |
| 10 | 79288 |
| 11 | 809515 |
| 12 | 1740735 |
| 13 | 17772468 |
| 14 | 38216892 |
| 15 | 390184791 |
| 16 | 839030899 |
| 17 | 8566292944 |
| 18 | 18420462896 |
| 19 | 188068259987 |
| 20 | 404411152823 |
| 21 | 4128935426780 |
| 22 | 8878624899220 |
| 23 | 90648511129183 |
| 24 | 194925336630027 |
| 25 | 1990138309415256 |
| 26 | 4279478780961384 |
| 27 | 43692394296006459 |
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