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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 30 |
| 3 | 154 |
| 4 | 788 |
| 5 | 4034 |
| 6 | 20650 |
| 7 | 105708 |
| 8 | 541122 |
| 9 | 2770018 |
| 10 | 14179796 |
| 11 | 72586754 |
| 12 | 371573530 |
| 13 | 1902094812 |
| 14 | 9736874082 |
| 15 | 49843318162 |
| 16 | 255149275268 |
| 17 | 1306115946338 |
| 18 | 6686042370634 |
| 19 | 34226029248972 |
| 20 | 175203956722818 |
[1,6,30,154,788,4034,20650,105708,541122,2770018, 14179796,72586754,371573530,1902094812,9736874082, 49843318162,255149275268,1306115946338, 6686042370634,34226029248972,175203956722818] |