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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 4 |
| 6 | 14 |
| 7 | 56 |
| 8 | 244 |
| 9 | 1140 |
| 10 | 5482 |
| 11 | 26886 |
| 12 | 134528 |
| 13 | 681944 |
| 14 | 3493524 |
| 15 | 18057208 |
| 16 | 94018056 |
| 17 | 492534414 |
| 18 | 2593760854 |
| 19 | 13720433802 |
| 20 | 72859816050 |
| 21 | 388218182456 |
| 22 | 2074683905712 |
| 23 | 11116464683746 |
| 24 | 59702675780296 |
| 25 | 321311045089704 |
| 26 | 1732487750419756 |
| 27 | 9357244742176372 |
| 28 | 50616284630194342 |
| 29 | 274180772642526672 |
| 30 | 1487084387418749912 |
[0,1,0,0,2,4,14,56,244,1140,5482,26886,134528, 681944,3493524,18057208,94018056,492534414, 2593760854,13720433802,72859816050,388218182456, 2074683905712,11116464683746,59702675780296, 321311045089704,1732487750419756,9357244742176372, 50616284630194342,274180772642526672, 1487084387418749912] |