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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 90 |
| 6 | 395 |
| 7 | 1823 |
| 8 | 8741 |
| 9 | 43193 |
| 10 | 218704 |
| 11 | 1129944 |
| 12 | 5937728 |
| 13 | 31656472 |
| 14 | 170892498 |
| 15 | 932625326 |
| 16 | 5138618526 |
| 17 | 28554124650 |
| 18 | 159874462032 |
| 19 | 901243508380 |
| 20 | 5111776163584 |
| 21 | 29155580007964 |
| 22 | 167139065156182 |
| 23 | 962618219420046 |
[1,1,2,6,22,90,395,1823,8741,43193,218704,1129944, 5937728,31656472,170892498,932625326,5138618526, 28554124650,159874462032,901243508380, 5111776163584,29155580007964,167139065156182, 962618219420046] |