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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 6 |
| 3 | 44 |
| 4 | 116 |
| 5 | 798 |
| 6 | 2090 |
| 7 | 14328 |
| 8 | 37512 |
| 9 | 257114 |
| 10 | 673134 |
| 11 | 4613732 |
| 12 | 12078908 |
| 13 | 82790070 |
| 14 | 216747218 |
| 15 | 1485607536 |
| 16 | 3889371024 |
| 17 | 26658145586 |
| 18 | 69791931222 |
| 19 | 478361013020 |
| 20 | 1252365390980 |
| 21 | 8583840088782 |
| 22 | 22472785106426 |
| 23 | 154030760585064 |
| 24 | 403257766524696 |
| 25 | 2763969850442378 |
[0,2,6,44,116,798,2090,14328,37512,257114,673134, 4613732,12078908,82790070,216747218,1485607536, 3889371024,26658145586,69791931222,478361013020, 1252365390980,8583840088782,22472785106426, 154030760585064,403257766524696,2763969850442378] |