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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 8 |
| 5 | 18 |
| 6 | 40 |
| 7 | 101 |
| 8 | 254 |
| 9 | 723 |
| 10 | 2064 |
| 11 | 6586 |
| 12 | 21143 |
| 13 | 74752 |
| 14 | 266078 |
| 15 | 1029983 |
| 16 | 4013425 |
| 17 | 16843526 |
| 18 | 71136112 |
| 19 | 321150717 |
| 20 | 1458636308 |
| 21 | 7038678613 |
| 22 | 34161890155 |
| 23 | 175261038904 |
| 24 | 904125989974 |
| 25 | 4909033438008 |
| 26 | 26795600521492 |
| 27 | 153376337926066 |
| 28 | 882391616100249 |
[1,1,2,4,8,18,40,101,254,723,2064,6586,21143, 74752,266078,1029983,4013425,16843526,71136112, 321150717,1458636308,7038678613,34161890155, 175261038904,904125989974,4909033438008, 26795600521492,153376337926066,882391616100249] |