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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 23 |
| 6 | 57 |
| 7 | 138 |
| 8 | 332 |
| 9 | 798 |
| 10 | 1920 |
| 11 | 4626 |
| 12 | 11157 |
| 13 | 26925 |
| 14 | 64997 |
| 15 | 156921 |
| 16 | 378861 |
| 17 | 914692 |
| 18 | 2208324 |
| 19 | 5331444 |
| 20 | 12871324 |
| 21 | 31074180 |
| 22 | 75019701 |
| 23 | 181113471 |
| 24 | 437246349 |
| 25 | 1055605659 |
| 26 | 2548456957 |
| 27 | 6152518758 |
| 28 | 14853493752 |
| 29 | 35859505946 |
| 30 | 86572506132 |
| 31 | 209004519918 |
[0,0,1,3,9,23,57,138,332,798,1920,4626,11157, 26925,64997,156921,378861,914692,2208324,5331444, 12871324,31074180,75019701,181113471,437246349, 1055605659,2548456957,6152518758,14853493752, 35859505946,86572506132,209004519918] |