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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 15 |
| 5 | 40 |
| 6 | 159 |
| 7 | 477 |
| 8 | 1955 |
| 9 | 6329 |
| 10 | 27222 |
| 11 | 93788 |
| 12 | 412542 |
| 13 | 1474861 |
| 14 | 6579591 |
| 15 | 24261248 |
| 16 | 109884004 |
| 17 | 415728514 |
| 18 | 1901528670 |
| 19 | 7332329870 |
| 20 | 33799600692 |
| 21 | 132520569402 |
| 22 | 615348352600 |
| 23 | 2447006155439 |
| 24 | 11425358766922 |
| 25 | 45967911583713 |
| 26 | 215656885564443 |
| 27 | 876735796325931 |
| 28 | 4130899475279367 |
[1,1,2,4,15,40,159,477,1955,6329,27222,93788, 412542,1474861,6579591,24261248,109884004, 415728514,1901528670,7332329870,33799600692, 132520569402,615348352600,2447006155439, 11425358766922,45967911583713,215656885564443, 876735796325931,4130899475279367] |