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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 51 |
| 3 | 452 |
| 4 | 3777 |
| 5 | 31074 |
| 6 | 250735 |
| 7 | 1993176 |
| 8 | 15640983 |
| 9 | 121378650 |
| 10 | 932738805 |
| 11 | 7105552308 |
| 12 | 53709133137 |
| 13 | 403124780178 |
| 14 | 3006420386499 |
| 15 | 22290321581448 |
| 16 | 164378277308862 |
| 17 | 1206180958964508 |
| 18 | 8810022165617086 |
| 19 | 64073173243207632 |
| 20 | 464122836576398454 |
| 21 | 3349321050668452460 |
[1,6,51,452,3777,31074,250735,1993176,15640983, 121378650,932738805,7105552308,53709133137, 403124780178,3006420386499,22290321581448, 164378277308862,1206180958964508,8810022165617086, 64073173243207632,464122836576398454, 3349321050668452460] |