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| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 86 |
| 3 | 515 |
| 4 | 3765 |
| 5 | 28942 |
| 6 | 231665 |
| 7 | 1906245 |
| 8 | 16000486 |
| 9 | 135790448 |
| 10 | 1158315893 |
| 11 | 9946076742 |
| 12 | 85823282205 |
| 13 | 743139183617 |
| 14 | 6451236349918 |
| 15 | 56119492560507 |
| 16 | 488978060398481 |
| 17 | 4265874977466648 |
| 18 | 37250999894755072 |
| 19 | 325525391487428809 |
[21,86,515,3765,28942,231665,1906245,16000486, 135790448,1158315893,9946076742,85823282205, 743139183617,6451236349918,56119492560507, 488978060398481,4265874977466648, 37250999894755072,325525391487428809] |