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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 36 |
| 3 | 168 |
| 4 | 696 |
| 5 | 2664 |
| 6 | 9720 |
| 7 | 34344 |
| 8 | 118584 |
| 9 | 402408 |
| 10 | 1347192 |
| 11 | 4461480 |
| 12 | 14644152 |
| 13 | 47711592 |
| 14 | 154472184 |
| 15 | 497428776 |
| 16 | 1594323000 |
| 17 | 5089079016 |
| 18 | 16185567096 |
| 19 | 51311691432 |
| 20 | 162200044728 |
| 21 | 511395045480 |
| 22 | 1608569870328 |
| 23 | 5048863812648 |
[0,36,168,696,2664,9720,34344,118584,402408, 1347192,4461480,14644152,47711592,154472184, 497428776,1594323000,5089079016,16185567096, 51311691432,162200044728,511395045480, 1608569870328,5048863812648] |