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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 25 |
| 5 | 121 |
| 6 | 361 |
| 7 | 3361 |
| 8 | 42001 |
| 9 | 275185 |
| 10 | 1819441 |
| 11 | 30777121 |
| 12 | 371238121 |
| 13 | 3057311401 |
| 14 | 44263763545 |
| 15 | 801096528961 |
| 16 | 9710981323681 |
| 17 | 125367419194081 |
| 18 | 2643123767954401 |
| 19 | 45840730383002305 |
| 20 | 646414025466298681 |
| 21 | 13258301279836276441 |
[1,1,1,1,25,121,361,3361,42001,275185,1819441, 30777121,371238121,3057311401,44263763545, 801096528961,9710981323681,125367419194081, 2643123767954401,45840730383002305, 646414025466298681,13258301279836276441] |