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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 16 |
| 7 | 80 |
| 8 | 473 |
| 9 | 2517 |
| 10 | 13431 |
| 11 | 69357 |
| 12 | 353943 |
| 13 | 1780894 |
| 14 | 8886254 |
| 15 | 44024308 |
| 16 | 217021967 |
| 17 | 1065653519 |
| 18 | 5217704239 |
| 19 | 25491204743 |
| 20 | 124335254416 |
| 21 | 605720277647 |
| 22 | 2948274685881 |
| 23 | 14341442951945 |
| 24 | 69732440151924 |
[0,0,0,0,1,2,16,80,473,2517,13431,69357,353943, 1780894,8886254,44024308,217021967,1065653519, 5217704239,25491204743,124335254416,605720277647, 2948274685881,14341442951945,69732440151924] |