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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 4 |
| 4 | 39 |
| 5 | 280 |
| 6 | 1815 |
| 7 | 11284 |
| 8 | 68859 |
| 9 | 416560 |
| 10 | 2509455 |
| 11 | 15086764 |
| 12 | 90610179 |
| 13 | 543928840 |
| 14 | 3264374295 |
| 15 | 19588645444 |
| 16 | 117539063499 |
| 17 | 705255937120 |
| 18 | 4231600258335 |
| 19 | 25389795391324 |
| 20 | 152339353740819 |
| 21 | 914037866361400 |
| 22 | 5484232429393575 |
| 23 | 32905410268988404 |
| 24 | 197432508689714139 |
[0,0,4,39,280,1815,11284,68859,416560,2509455, 15086764,90610179,543928840,3264374295, 19588645444,117539063499,705255937120, 4231600258335,25389795391324,152339353740819, 914037866361400,5484232429393575, 32905410268988404,197432508689714139] |