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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 4 |
| 6 | 20 |
| 7 | 115 |
| 8 | 787 |
| 9 | 6184 |
| 10 | 54888 |
| 11 | 542805 |
| 12 | 5916725 |
| 13 | 70463900 |
| 14 | 910167596 |
| 15 | 12672415015 |
| 16 | 189181881575 |
| 17 | 3014307220880 |
| 18 | 51054940726928 |
| 19 | 915987174021609 |
| 20 | 17352888926841897 |
| 21 | 346144782915314740 |
| 22 | 7251738265074465220 |
| 23 | 159193007549552845339 |
| 24 | 3654204694819144118651 |
[0,0,1,1,4,20,115,787,6184,54888,542805,5916725, 70463900,910167596,12672415015,189181881575, 3014307220880,51054940726928,915987174021609, 17352888926841897,346144782915314740, 7251738265074465220,159193007549552845339, 3654204694819144118651] |