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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 16 |
| 5 | 45 |
| 6 | 130 |
| 7 | 377 |
| 8 | 1088 |
| 9 | 3145 |
| 10 | 9090 |
| 11 | 26269 |
| 12 | 75920 |
| 13 | 219413 |
| 14 | 634114 |
| 15 | 1832625 |
| 16 | 5296384 |
| 17 | 15306833 |
| 18 | 44237570 |
| 19 | 127848949 |
| 20 | 369490320 |
| 21 | 1067846845 |
| 22 | 3086134658 |
| 23 | 8919094697 |
| 24 | 25776662080 |
| 25 | 74495936025 |
| 26 | 215297250946 |
| 27 | 622220603405 |
[0,1,2,5,16,45,130,377,1088,3145,9090,26269,75920, 219413,634114,1832625,5296384,15306833,44237570, 127848949,369490320,1067846845,3086134658, 8919094697,25776662080,74495936025,215297250946, 622220603405] |