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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 20 |
| 3 | 54 |
| 4 | 136 |
| 5 | 334 |
| 6 | 812 |
| 7 | 1966 |
| 8 | 4752 |
| 9 | 11478 |
| 10 | 27716 |
| 11 | 66918 |
| 12 | 161560 |
| 13 | 390046 |
| 14 | 941660 |
| 15 | 2273374 |
| 16 | 5488416 |
| 17 | 13250214 |
| 18 | 31988852 |
| 19 | 77227926 |
| 20 | 186444712 |
| 21 | 450117358 |
| 22 | 1086679436 |
| 23 | 2623476238 |
| 24 | 6333631920 |
| 25 | 15290740086 |
| 26 | 36915112100 |
| 27 | 89120964294 |
| 28 | 215157040696 |
| 29 | 519435045694 |
| 30 | 1254027132092 |
[1,6,20,54,136,334,812,1966,4752,11478,27716, 66918,161560,390046,941660,2273374,5488416, 13250214,31988852,77227926,186444712,450117358, 1086679436,2623476238,6333631920,15290740086, 36915112100,89120964294,215157040696,519435045694, 1254027132092] |