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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 11 |
| 4 | 34 |
| 5 | 84 |
| 6 | 225 |
| 7 | 584 |
| 8 | 1534 |
| 9 | 4011 |
| 10 | 10506 |
| 11 | 27500 |
| 12 | 72001 |
| 13 | 188496 |
| 14 | 493494 |
| 15 | 1291979 |
| 16 | 3382450 |
| 17 | 8855364 |
| 18 | 23183649 |
| 19 | 60695576 |
| 20 | 158903086 |
| 21 | 416013675 |
| 22 | 1089137946 |
| 23 | 2851400156 |
| 24 | 7465062529 |
| 25 | 19543787424 |
| 26 | 51166299750 |
| 27 | 133955111819 |
| 28 | 350699035714 |
| 29 | 918141995316 |
[1,0,6,11,34,84,225,584,1534,4011,10506,27500, 72001,188496,493494,1291979,3382450,8855364, 23183649,60695576,158903086,416013675,1089137946, 2851400156,7465062529,19543787424,51166299750, 133955111819,350699035714,918141995316] |