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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 66 |
| 4 | 1577 |
| 5 | 18218 |
| 6 | 135550 |
| 7 | 738236 |
| 8 | 3207785 |
| 9 | 11714718 |
| 10 | 37347144 |
| 11 | 106499470 |
| 12 | 277489886 |
| 13 | 668981686 |
| 14 | 1512360404 |
| 15 | 3228797252 |
| 16 | 6570019945 |
| 17 | 12793050456 |
| 18 | 24001960051 |
| 19 | 43483452090 |
| 20 | 76485144056 |
| 21 | 130752372320 |
| 22 | 218220937122 |
| 23 | 355664809556 |
| 24 | 568293832670 |
| 25 | 889969136158 |
[0,1,66,1577,18218,135550,738236,3207785,11714718, 37347144,106499470,277489886,668981686,1512360404, 3228797252,6570019945,12793050456,24001960051, 43483452090,76485144056,130752372320,218220937122, 355664809556,568293832670,889969136158] |