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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 55 |
| 3 | 209 |
| 4 | 6336 |
| 5 | 30305 |
| 6 | 817991 |
| 7 | 4140081 |
| 8 | 108435745 |
| 9 | 557568000 |
| 10 | 14479521761 |
| 11 | 74795194705 |
| 12 | 1937528668711 |
| 13 | 10021992194369 |
| 14 | 259423766712000 |
| 15 | 1342421467113969 |
| 16 | 34741645659770711 |
| 17 | 179796299139278305 |
| 18 | 4652799879944138561 |
[1,1,55,209,6336,30305,817991,4140081,108435745, 557568000,14479521761,74795194705,1937528668711, 10021992194369,259423766712000,1342421467113969, 34741645659770711,179796299139278305, 4652799879944138561] |