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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 29 |
| 3 | 231 |
| 4 | 1926 |
| 5 | 16491 |
| 6 | 143683 |
| 7 | 1267395 |
| 8 | 11282393 |
| 9 | 101151544 |
| 10 | 912011633 |
| 11 | 8260998772 |
| 12 | 75115815749 |
| 13 | 685232639419 |
| 14 | 6268299350776 |
| 15 | 57478389714473 |
| 16 | 528167137069958 |
| 17 | 4862304525663579 |
| 18 | 44836026545219765 |
| 19 | 414048025058547788 |
| 20 | 3828677665694353049 |
[1,4,29,231,1926,16491,143683,1267395,11282393, 101151544,912011633,8260998772,75115815749, 685232639419,6268299350776,57478389714473, 528167137069958,4862304525663579, 44836026545219765,414048025058547788, 3828677665694353049] |