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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 10 |
| 3 | 25 |
| 4 | 66 |
| 5 | 154 |
| 6 | 392 |
| 7 | 882 |
| 8 | 2180 |
| 9 | 4796 |
| 10 | 11640 |
| 11 | 25220 |
| 12 | 60424 |
| 13 | 129480 |
| 14 | 307264 |
| 15 | 652936 |
| 16 | 1538064 |
| 17 | 3247024 |
| 18 | 7604000 |
| 19 | 15968400 |
| 20 | 37217312 |
| 21 | 77818016 |
| 22 | 180652416 |
| 23 | 376359200 |
| 24 | 870795328 |
| 25 | 1808574912 |
| 26 | 4172640640 |
| 27 | 8643327040 |
[1,3,10,25,66,154,392,882,2180,4796,11640,25220, 60424,129480,307264,652936,1538064,3247024, 7604000,15968400,37217312,77818016,180652416, 376359200,870795328,1808574912,4172640640, 8643327040] |