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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 40 |
| 5 | 267 |
| 6 | 1350 |
| 7 | 5936 |
| 8 | 23565 |
| 9 | 84912 |
| 10 | 278422 |
| 11 | 835824 |
| 12 | 2316601 |
| 13 | 5980937 |
| 14 | 14503972 |
| 15 | 33282396 |
| 16 | 72732358 |
| 17 | 152195016 |
| 18 | 306378420 |
| 19 | 595704701 |
| 20 | 1122541470 |
| 21 | 2056128263 |
| 22 | 3670127802 |
| 23 | 6398217740 |
| 24 | 10915088955 |
| 25 | 18252749400 |
| 26 | 29965289850 |
[0,0,3,40,267,1350,5936,23565,84912,278422,835824, 2316601,5980937,14503972,33282396,72732358, 152195016,306378420,595704701,1122541470, 2056128263,3670127802,6398217740,10915088955, 18252749400,29965289850] |