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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 17 |
| 5 | 50 |
| 6 | 138 |
| 7 | 370 |
| 8 | 979 |
| 9 | 2575 |
| 10 | 6755 |
| 11 | 17700 |
| 12 | 46356 |
| 13 | 121380 |
| 14 | 317797 |
| 15 | 832025 |
| 16 | 2178293 |
| 17 | 5702870 |
| 18 | 14930334 |
| 19 | 39088150 |
| 20 | 102334135 |
| 21 | 267914275 |
| 22 | 701408711 |
| 23 | 1836311880 |
| 24 | 4807526952 |
| 25 | 12586269000 |
| 26 | 32951280073 |
| 27 | 86267571245 |
| 28 | 225851433689 |
| 29 | 591286729850 |
[0,0,1,5,17,50,138,370,979,2575,6755,17700,46356, 121380,317797,832025,2178293,5702870,14930334, 39088150,102334135,267914275,701408711,1836311880, 4807526952,12586269000,32951280073,86267571245, 225851433689,591286729850] |