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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 38 |
| 5 | 120 |
| 6 | 514 |
| 7 | 1787 |
| 8 | 8042 |
| 9 | 30024 |
| 10 | 137224 |
| 11 | 530796 |
| 12 | 2480856 |
| 13 | 9918516 |
| 14 | 46702784 |
| 15 | 190374471 |
| 16 | 906997854 |
| 17 | 3769136982 |
| 18 | 18033009962 |
| 19 | 75864970010 |
| 20 | 365546041018 |
| 21 | 1557303595620 |
| 22 | 7524069805854 |
| 23 | 32328005954926 |
| 24 | 156919659652734 |
| 25 | 680199365173406 |
| 26 | 3307922174834418 |
| 27 | 14428871521016760 |
| 28 | 70397383520857038 |
[1,1,4,9,38,120,514,1787,8042,30024,137224,530796, 2480856,9918516,46702784,190374471,906997854, 3769136982,18033009962,75864970010,365546041018, 1557303595620,7524069805854,32328005954926, 156919659652734,680199365173406,3307922174834418, 14428871521016760,70397383520857038] |