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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 42 |
| 4 | 744 |
| 5 | 18570 |
| 6 | 596929 |
| 7 | 23457763 |
| 8 | 1089601420 |
| 9 | 58424516424 |
| 10 | 3553205095552 |
| 11 | 241765128267597 |
| 12 | 18202737707568180 |
| 13 | 1502857964050898494 |
| 14 | 135033771405912550765 |
| 15 | 13119213786776385900734 |
| 16 | 1370572549521961522812200 |
| 17 | 153224265349198540163190599 |
| 18 | 18253426026439076436840194131 |
| 19 | 2308479498698233016622014842489 |
[1,1,4,42,744,18570,596929,23457763,1089601420, 58424516424,3553205095552,241765128267597, 18202737707568180,1502857964050898494, 135033771405912550765,13119213786776385900734, 1370572549521961522812200, 153224265349198540163190599, 18253426026439076436840194131, 2308479498698233016622014842489] |