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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 34 |
| 5 | 99 |
| 6 | 308 |
| 7 | 1040 |
| 8 | 3820 |
| 9 | 15197 |
| 10 | 65060 |
| 11 | 297828 |
| 12 | 1449742 |
| 13 | 7468527 |
| 14 | 40555732 |
| 15 | 231335944 |
| 16 | 1381989864 |
| 17 | 8623700793 |
| 18 | 56078446596 |
| 19 | 379233142780 |
| 20 | 2662013133274 |
| 21 | 19362917621979 |
| 22 | 145719550012276 |
| 23 | 1133023004941248 |
| 24 | 9090156910550084 |
| 25 | 75161929739797493 |
| 26 | 639793220877941476 |
[0,1,4,12,34,99,308,1040,3820,15197,65060,297828, 1449742,7468527,40555732,231335944,1381989864, 8623700793,56078446596,379233142780,2662013133274, 19362917621979,145719550012276,1133023004941248, 9090156910550084,75161929739797493, 639793220877941476] |