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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 28 |
| 5 | 88 |
| 6 | 284 |
| 7 | 931 |
| 8 | 3109 |
| 9 | 10532 |
| 10 | 36162 |
| 11 | 125546 |
| 12 | 440201 |
| 13 | 1556519 |
| 14 | 5544715 |
| 15 | 19879791 |
| 16 | 71685522 |
| 17 | 259809731 |
| 18 | 945913555 |
| 19 | 3457947627 |
| 20 | 12687782600 |
| 21 | 46709518473 |
| 22 | 172484216742 |
| 23 | 638712762962 |
| 24 | 2371241532557 |
| 25 | 8824154454401 |
| 26 | 32909438791706 |
| 27 | 122984173008460 |
[1,1,3,9,28,88,284,931,3109,10532,36162,125546, 440201,1556519,5544715,19879791,71685522, 259809731,945913555,3457947627,12687782600, 46709518473,172484216742,638712762962, 2371241532557,8824154454401,32909438791706, 122984173008460] |