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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 10 |
| 6 | 40 |
| 7 | 171 |
| 8 | 831 |
| 9 | 4147 |
| 10 | 21822 |
| 11 | 117062 |
| 12 | 642600 |
| 13 | 3582322 |
| 14 | 20256885 |
| 15 | 115888201 |
| 16 | 669911568 |
| 17 | 3907720521 |
| 18 | 22979343010 |
| 19 | 136107859377 |
| 20 | 811430160282 |
| 21 | 4866004426320 |
| 22 | 29337068299728 |
| 23 | 177738920836446 |
| 24 | 1081668278379000 |
| 25 | 6609923004626478 |
| 26 | 40546403939165805 |
[1,1,1,4,10,40,171,831,4147,21822,117062,642600, 3582322,20256885,115888201,669911568,3907720521, 22979343010,136107859377,811430160282, 4866004426320,29337068299728,177738920836446, 1081668278379000,6609923004626478, 40546403939165805] |