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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 13 |
| 6 | 146 |
| 7 | 826 |
| 8 | 44808 |
| 9 | 1074557 |
| 10 | 155741296 |
| 11 | 10381741786 |
| 12 | 6939251270348 |
| 13 | 2203360264480750 |
| 14 | 4186526735251514044 |
| 15 | 3747344007864300197810 |
| 16 | 35041787059621536192399824 |
| 17 | 156277111373298355107598128061 |
| 18 | 4142122641757597729416733678931968 |
[1,1,1,4,13,146,826,44808,1074557,155741296, 10381741786,6939251270348,2203360264480750, 4186526735251514044,3747344007864300197810, 35041787059621536192399824, 156277111373298355107598128061, 4142122641757597729416733678931968] |