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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 21 |
| 5 | 72 |
| 6 | 257 |
| 7 | 998 |
| 8 | 3988 |
| 9 | 16064 |
| 10 | 65734 |
| 11 | 273541 |
| 12 | 1151184 |
| 13 | 4886946 |
| 14 | 20916523 |
| 15 | 90181047 |
| 16 | 391230537 |
| 17 | 1706503782 |
| 18 | 7480000600 |
| 19 | 32930469730 |
| 20 | 145546039760 |
| 21 | 645574246834 |
| 22 | 2872745389578 |
| 23 | 12821285282360 |
| 24 | 57377599801569 |
| 25 | 257416078950987 |
| 26 | 1157519956026736 |
| 27 | 5216112572700566 |
[1,1,2,5,21,72,257,998,3988,16064,65734,273541, 1151184,4886946,20916523,90181047,391230537, 1706503782,7480000600,32930469730,145546039760, 645574246834,2872745389578,12821285282360, 57377599801569,257416078950987,1157519956026736, 5216112572700566] |