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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 24 |
| 3 | 92 |
| 4 | 340 |
| 5 | 1236 |
| 6 | 4452 |
| 7 | 15956 |
| 8 | 57028 |
| 9 | 203508 |
| 10 | 725604 |
| 11 | 2585876 |
| 12 | 9212932 |
| 13 | 32818740 |
| 14 | 116898468 |
| 15 | 416365652 |
| 16 | 1482959428 |
| 17 | 5281740660 |
| 18 | 18811402980 |
| 19 | 66998214548 |
| 20 | 238618498180 |
| 21 | 849854020788 |
| 22 | 3026803253028 |
| 23 | 10780126189268 |
| 24 | 38394001851076 |
| 25 | 136742291486196 |
[1,6,24,92,340,1236,4452,15956,57028,203508, 725604,2585876,9212932,32818740,116898468, 416365652,1482959428,5281740660,18811402980, 66998214548,238618498180,849854020788, 3026803253028,10780126189268,38394001851076, 136742291486196] |