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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 14 |
| 3 | 48 |
| 4 | 137 |
| 5 | 380 |
| 6 | 998 |
| 7 | 2488 |
| 8 | 5996 |
| 9 | 14020 |
| 10 | 31868 |
| 11 | 70616 |
| 12 | 153389 |
| 13 | 326248 |
| 14 | 681914 |
| 15 | 1402880 |
| 16 | 2841769 |
| 17 | 5678316 |
| 18 | 11201956 |
| 19 | 21833480 |
| 20 | 42081245 |
| 21 | 80264752 |
| 22 | 151572328 |
| 23 | 283577152 |
| 24 | 525894397 |
| 25 | 967100700 |
| 26 | 1764378830 |
| 27 | 3194682272 |
| 28 | 5742739237 |
| 29 | 10252117308 |
| 30 | 18182247316 |
[1,4,14,48,137,380,998,2488,5996,14020,31868, 70616,153389,326248,681914,1402880,2841769, 5678316,11201956,21833480,42081245,80264752, 151572328,283577152,525894397,967100700, 1764378830,3194682272,5742739237,10252117308, 18182247316] |