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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 | 9284332201 |
| 14 | 131442054745 |
| 15 | 1454933712961 |
| 16 | 34120902859681 |
| 17 | 851562584890081 |
| 18 | 12300037440760801 |
| 19 | 187928965721651905 |
| 20 | 6019555345508794681 |
| 21 | 130768735411230580441 |
[1,1,1,1,25,121,361,3361,42001,275185,1819441, 30777121,371238121,9284332201,131442054745, 1454933712961,34120902859681,851562584890081, 12300037440760801,187928965721651905, 6019555345508794681,130768735411230580441] |