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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 15 |
| 4 | 37 |
| 5 | 90 |
| 6 | 218 |
| 7 | 527 |
| 8 | 1273 |
| 9 | 3074 |
| 10 | 7422 |
| 11 | 17919 |
| 12 | 43261 |
| 13 | 104442 |
| 14 | 252146 |
| 15 | 608735 |
| 16 | 1469617 |
| 17 | 3547970 |
| 18 | 8565558 |
| 19 | 20679087 |
| 20 | 49923733 |
| 21 | 120526554 |
| 22 | 290976842 |
| 23 | 702480239 |
| 24 | 1695937321 |
| 25 | 4094354882 |
| 26 | 9884647086 |
| 27 | 23863649055 |
| 28 | 57611945197 |
[1,2,6,15,37,90,218,527,1273,3074,7422,17919, 43261,104442,252146,608735,1469617,3547970, 8565558,20679087,49923733,120526554,290976842, 702480239,1695937321,4094354882,9884647086, 23863649055,57611945197] |