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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 11 |
| 5 | 24 |
| 6 | 56 |
| 7 | 129 |
| 8 | 300 |
| 9 | 698 |
| 10 | 1623 |
| 11 | 3773 |
| 12 | 8771 |
| 13 | 20390 |
| 14 | 47401 |
| 15 | 110194 |
| 16 | 256170 |
| 17 | 595523 |
| 18 | 1384423 |
| 19 | 3218393 |
| 20 | 7481856 |
| 21 | 17393205 |
| 22 | 40434296 |
| 23 | 93998334 |
| 24 | 218519615 |
| 25 | 507996473 |
| 26 | 1180948523 |
| 27 | 2745372238 |
| 28 | 6382216141 |
| 29 | 14836852470 |
| 30 | 34491497366 |
[1,1,1,4,11,24,56,129,300,698,1623,3773,8771, 20390,47401,110194,256170,595523,1384423,3218393, 7481856,17393205,40434296,93998334,218519615, 507996473,1180948523,2745372238,6382216141, 14836852470,34491497366] |