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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 21 |
| 4 | 93 |
| 5 | 334 |
| 6 | 1536 |
| 7 | 5867 |
| 8 | 28047 |
| 9 | 112618 |
| 10 | 542814 |
| 11 | 2233452 |
| 12 | 10915934 |
| 13 | 45965645 |
| 14 | 225308120 |
| 15 | 961377360 |
| 16 | 4743469916 |
| 17 | 20511319674 |
| 18 | 101331875971 |
| 19 | 441859544548 |
| 20 | 2190789707577 |
| 21 | 9635965245969 |
| 22 | 47806098871455 |
| 23 | 211501235721331 |
| 24 | 1051569451113436 |
| 25 | 4680667747964805 |
| 26 | 23279726523079784 |
| 27 | 104070299439210842 |
[1,2,7,21,93,334,1536,5867,28047,112618,542814, 2233452,10915934,45965645,225308120,961377360, 4743469916,20511319674,101331875971,441859544548, 2190789707577,9635965245969,47806098871455, 211501235721331,1051569451113436,4680667747964805, 23279726523079784,104070299439210842] |