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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 7 |
| 5 | 22 |
| 6 | 64 |
| 7 | 196 |
| 8 | 574 |
| 9 | 1762 |
| 10 | 5379 |
| 11 | 16378 |
| 12 | 49380 |
| 13 | 148892 |
| 14 | 449004 |
| 15 | 1353718 |
| 16 | 4076150 |
| 17 | 12267160 |
| 18 | 36903433 |
| 19 | 110979048 |
| 20 | 333628384 |
| 21 | 1002722482 |
| 22 | 3013085711 |
| 23 | 9052404522 |
| 24 | 27192329061 |
| 25 | 81671691634 |
| 26 | 245271884478 |
| 27 | 736513920180 |
| 28 | 2211445194899 |
| 29 | 6639545054310 |
[0,0,0,2,7,22,64,196,574,1762,5379,16378,49380, 148892,449004,1353718,4076150,12267160,36903433, 110979048,333628384,1002722482,3013085711, 9052404522,27192329061,81671691634,245271884478, 736513920180,2211445194899,6639545054310] |