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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 5 |
| 3 | 7 |
| 4 | 27 |
| 5 | 66 |
| 6 | 195 |
| 7 | 540 |
| 8 | 1547 |
| 9 | 4408 |
| 10 | 12663 |
| 11 | 36455 |
| 12 | 105325 |
| 13 | 305046 |
| 14 | 885573 |
| 15 | 2576007 |
| 16 | 7506675 |
| 17 | 21909720 |
| 18 | 64039119 |
| 19 | 187418205 |
| 20 | 549141249 |
| 21 | 1610708190 |
| 22 | 4729015305 |
| 23 | 13896677718 |
| 24 | 40870234629 |
| 25 | 120290710176 |
| 26 | 354292339625 |
| 27 | 1044178154305 |
[1,0,5,7,27,66,195,540,1547,4408,12663,36455, 105325,305046,885573,2576007,7506675,21909720, 64039119,187418205,549141249,1610708190, 4729015305,13896677718,40870234629,120290710176, 354292339625,1044178154305] |