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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 25 |
| 4 | 120 |
| 5 | 581 |
| 6 | 2877 |
| 7 | 14421 |
| 8 | 72996 |
| 9 | 372229 |
| 10 | 1909336 |
| 11 | 9840909 |
| 12 | 50923041 |
| 13 | 264391973 |
| 14 | 1376654747 |
| 15 | 7185811685 |
| 16 | 37589283916 |
| 17 | 197005160825 |
| 18 | 1034244838815 |
| 19 | 5437798710585 |
| 20 | 28629290831670 |
| 21 | 150913830095445 |
| 22 | 796396974477495 |
| 23 | 4206974157985845 |
| 24 | 22243990866224505 |
[1,6,25,120,581,2877,14421,72996,372229,1909336, 9840909,50923041,264391973,1376654747,7185811685, 37589283916,197005160825,1034244838815, 5437798710585,28629290831670,150913830095445, 796396974477495,4206974157985845, 22243990866224505] |