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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 28 |
| 4 | 118 |
| 5 | 380 |
| 6 | 1508 |
| 7 | 5240 |
| 8 | 20326 |
| 9 | 73836 |
| 10 | 284396 |
| 11 | 1061128 |
| 12 | 4085820 |
| 13 | 15500120 |
| 14 | 59820040 |
| 15 | 229366768 |
| 16 | 887943046 |
| 17 | 3428967500 |
| 18 | 13315684764 |
| 19 | 51678099304 |
| 20 | 201246353492 |
| 21 | 783890932488 |
| 22 | 3060144292600 |
| 23 | 11953056489104 |
[1,2,10,28,118,380,1508,5240,20326,73836,284396, 1061128,4085820,15500120,59820040,229366768, 887943046,3428967500,13315684764,51678099304, 201246353492,783890932488,3060144292600, 11953056489104] |