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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 56 |
| 3 | 455 |
| 4 | 3696 |
| 5 | 30023 |
| 6 | 243880 |
| 7 | 1981063 |
| 8 | 16092384 |
| 9 | 130720135 |
| 10 | 1061853464 |
| 11 | 8625547847 |
| 12 | 70066236240 |
| 13 | 569155437767 |
| 14 | 4623309738376 |
| 15 | 37555633344775 |
| 16 | 305068376496576 |
| 17 | 2478102645317383 |
| 18 | 20129889539035640 |
| 19 | 163517218957602503 |
[1,7,56,455,3696,30023,243880,1981063,16092384, 130720135,1061853464,8625547847,70066236240, 569155437767,4623309738376,37555633344775, 305068376496576,2478102645317383, 20129889539035640,163517218957602503] |