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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 25 |
| 4 | 244 |
| 5 | 3380 |
| 6 | 62133 |
| 7 | 1440382 |
| 8 | 40673705 |
| 9 | 1364815169 |
| 10 | 53415511305 |
| 11 | 2402797049419 |
| 12 | 122751622204827 |
| 13 | 7051227704802797 |
| 14 | 451598420376965588 |
| 15 | 32013004761567761223 |
| 16 | 2495936511077175475140 |
| 17 | 212840593118800653411004 |
| 18 | 19753575434503894710824531 |
[1,1,4,25,244,3380,62133,1440382,40673705, 1364815169,53415511305,2402797049419, 122751622204827,7051227704802797, 451598420376965588,32013004761567761223, 2495936511077175475140,212840593118800653411004, 19753575434503894710824531] |