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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 26 |
| 6 | 74 |
| 7 | 218 |
| 8 | 668 |
| 9 | 2096 |
| 10 | 6726 |
| 11 | 21946 |
| 12 | 72666 |
| 13 | 243504 |
| 14 | 824528 |
| 15 | 2816854 |
| 16 | 9698520 |
| 17 | 33620626 |
| 18 | 117254340 |
| 19 | 411135452 |
| 20 | 1448544666 |
| 21 | 5125796448 |
| 22 | 18209367238 |
| 23 | 64919822556 |
| 24 | 232206203152 |
| 25 | 833040115596 |
| 26 | 2996741699470 |
| 27 | 10807658186756 |
| 28 | 39068847237770 |
[1,1,2,4,10,26,74,218,668,2096,6726,21946,72666, 243504,824528,2816854,9698520,33620626,117254340, 411135452,1448544666,5125796448,18209367238, 64919822556,232206203152,833040115596, 2996741699470,10807658186756,39068847237770] |