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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 10 |
| 4 | 28 |
| 5 | 76 |
| 6 | 208 |
| 7 | 568 |
| 8 | 1552 |
| 9 | 4240 |
| 10 | 11584 |
| 11 | 31648 |
| 12 | 86464 |
| 13 | 236224 |
| 14 | 645376 |
| 15 | 1763200 |
| 16 | 4817152 |
| 17 | 13160704 |
| 18 | 35955712 |
| 19 | 98232832 |
| 20 | 268377088 |
| 21 | 733219840 |
| 22 | 2003193856 |
| 23 | 5472827392 |
| 24 | 14952042496 |
| 25 | 40849739776 |
[1,1,4,10,28,76,208,568,1552,4240,11584,31648, 86464,236224,645376,1763200,4817152,13160704, 35955712,98232832,268377088,733219840,2003193856, 5472827392,14952042496,40849739776] |