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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 10 |
| 5 | 25 |
| 6 | 71 |
| 7 | 196 |
| 8 | 554 |
| 9 | 1569 |
| 10 | 4477 |
| 11 | 12826 |
| 12 | 36895 |
| 13 | 106470 |
| 14 | 308114 |
| 15 | 893803 |
| 16 | 2598314 |
| 17 | 7567465 |
| 18 | 22076405 |
| 19 | 64498426 |
| 20 | 188689685 |
| 21 | 552675364 |
| 22 | 1620567764 |
| 23 | 4756614061 |
| 24 | 13974168191 |
| 25 | 41088418150 |
| 26 | 120906613076 |
| 27 | 356035078101 |
| 28 | 1049120176954 |
[1,0,2,3,10,25,71,196,554,1569,4477,12826,36895, 106470,308114,893803,2598314,7567465,22076405, 64498426,188689685,552675364,1620567764, 4756614061,13974168191,41088418150,120906613076, 356035078101,1049120176954] |